The rapid detection and identification of organic macromolecules can be realized by using the unique fringerprint spectrum of the terahertz band, but the measurement of terahertz absorption spectrum of trace analyte is still challenging. We proposed a detection scheme of enhancement of terahertz absorption spectrum for trace organic analyte based on angle multiplexing of the dielectric metasurface. The substrate and the cross-unit structure of metasurface are both high-resistance silicon which has high-Q resonances. The resonance frequency of the metasurface under terahertz incident with different angles can cover 0.50-0.57 THz. When a lactose film with the thickness of 0.5-2.5 μm as analyte is placed on the metasurface, the amplitude of the resonance peak corresponding to each incident angle changes greatly with the absorption spectrum of the analyte. The enhanced absorption spectrum built by the resonance frequencies envelope is 82.59 times larger than that without the cross-unit structure. The simulation results show that the metasurface has great potential to enhance the terahertz absorption spectrum through angle multiplexing, and it can be used to detect trace organic substances with different characteristic peaks after optimized design.