Diamond nanopillars can improve the photon emission efficiency of color centers and have a focusing effect on the emitted photons. By using the time-domain finite-difference method, the effects of structural changes such as diameter, height and color center position of diamond nanopillar on parameters such as Purcell factor, photon transmittance and photon extraction efficiency of color centers in the nanopillars are studied in this work, the mechanism of the nanopillar structure enhancing the luminescence of color centers is discussed, and the optimal nanopillar structure parameters are explored to obtain the maximal total fluorescence collection of color centers. It is found that the total fluorescence collection of color centers under the optimal structure is 17 times higher than that of bulk diamond, and can be effectively collected by a microscope with numerical apertureN_A=0.95. Among the structural parameters, the size error of nanopillar diameter has the greatest influence on fluorescence collection, but it can also be more than 13 times than that of bulk diamond even in the range of ±20 nm. This study provides a foundation for the design and preparation of diamond color-centered luminescence-enhanced structure.