When a planar wave illuminates the microstructure of a dielectric material, it will appear in the shadow surface of the high-intensity energy gathering area and radiate to the far field, which is the photonic nanojet effect. Due to its strong focusing and ability to break through diffraction limits,the photonic nanojet has broad application prospects in the field of biological detection and optical characterization. Since the concept of photonic nanojet was proposed in 2004, researchers have explored the factors influencing the performance characteristics of photonic nanocrystals by changing various parameters. The results show that the formation of photonic nanocrystals is related to the microstructure shape, the incident wavelength and the ratio of the microstructure to the refractive index of the background. Although different photonic nanojets can be obtained in relevant studies, dynamic regulation can not be achieved. Liquid crystal has entered the field of scholars studying the phenomenon of photonic nanojet because of its tunable external field, providing more possibilities for subsequent studies. Subsequently, the method of combining with liquid crystal to change refractive index contrast and realize tunable photonic nanocrystals is proposed successively. However, most of the existing liquid crystal photonic nanojet is developed around the microsphere structure. When considering the microstructure of liquid crystal combined with the gradient profile of heterogeneous materials, the tunability of its light field deserves further study. This paper proposes a photonic nanojet optical element coupled with space light modulation of heterogeneous material bilayer micropyramid structure, which uses the liquid crystal as the background medium, and changes the rotation angle of the liquid crystal molecule by applying external forces to reduce the ratio of the microstructure to the refractive index of the background, and to realize the dynamic adjustment of the photonic nanojet. The Finite Difference Time Domain (FDTD) method is used for simulation. The fundamental law of photonic nanojet performance characteristics changes when the contrast between the microstructure and the background refractive index is reduced. The results show that the effect of reducing refractive index contrast on the photonic nanojet of heterogeneous material bilayer micropyramid structure is mainly reflected in the lateral width and focusing efficiency at the focal point, the focal length increases, the energy shifts backwards and the multifocus appear. The focal length of PNJ changes from 6.1λ to 22.3λ, and the decay length is up to 36.5λ. Comparing with the photonic nanojet generated by the bilayer microsphere structure coupled with liquid crystal, the decay length is improved by 10λ. With the reduction of the ratio of the refractive index of the microstructure to the background medium, the full width at half maximum increases, and the adjustment range of the focusing efficiency can reach 16.9% to 43.2%, when the focus gradually moves away from the microstructure, and the energy is transmitted to the far field. By comparing microstructures without and with liquid crystals, it can be concluded that the intensity and half-height full width of the microstructure light field without liquid crystal are similar to those with the presence of liquid crystal, and the focal length and attenuation length are much smaller than those with the presence of liquid crystal. Moreover, liquid crystal can give diversity to the light field and has the ability to regulate it. The spherical MIE scattering theory agrees with the results in this paper. With the help of liquid crystal as a spatial light modulation method, the bilayer micropyramid structure photonic nanojet realizes a wide range of focal length adjustment and ultra-long propagation length, providing theoretical support for the application of photonic nanojet in photoelectric detection and optical capture.