With the development of optoelectronic countermeasures and ultrashort pulse laser technology, the study of the interaction between ultrashort pulse laser and monocrystalline silicon has a very important theoretical and practical significance. In order to further clarify the damage mechanism of 532 nm picosecond pulsed laser on monocrystalline silicon, we have conducted an experimental study to measure the damage threshold, clarify the damage mechanism, and discuss the pulse accumulation effect at low flux. Firstly, using a laser with a wavelength of 532 nm, a pulse width of 30 ps and a metallurgical microscope based on the 1-on-1 laser damage test method, the zero damage probability threshold is determined to be 0.52 J/cm². Secondly, the damage effect of a picosecond laser irradiated on monocrystalline silicon was studied under different laser fluxes, and it was found that the damage of 532 nm picosecond laser to monocrystalline silicon is manifested as heated-effect damage and plasma impact damage. The increase in energy density can be divided into three stages according to the main damage mechanism: thermal effect (0.52~3 J/cm²), thermal ablation (3~50 J/cm²) and plasma effect (>50 J/cm²), and the damaged areas are corresponded to different growth laws with the laser energy density, respectively. Finally, an experiment for the multi-pulse cumulative effect was carried out at a low laser flux and it was found that at a laser energy density of 0.52 J/cm², the surface was irradiated continuously for 16 shots. The formation of a heat-affected zone confirms that the cumulative effect of multiple pulses can lower the laser damage threshold on monocrystalline silicon.