In order to study the crystal nucleation process of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), the CrystlScan multi-channel crystallizer was used to measure the crystallization nucleation induction period of LLM-105 in antisolvent system. The influence of supersaturation on the nucleation of LLM-105 was studied by using the induction period measurement method, and the important nucleation parameters were calculated by the classic nucleation theory. The results show that the induction period of anti-solvent crystallization of LLM-105 decreases with increasing supersaturation. When the supersaturation ratio S<2.53, heterogeneous nucleation was mainly observed, the interfacial tension γ value is 6.67717×10^-23 J·m^-2, and the surface entropy factor f value is 1.49; when S>2.53, the homogeneous nucleation was mainly achieved, the interfacial tension γ value is 9.89842×10^-23 J·m^-2 and the surface entropy factor f value is 2.23. The surface entropy factor values were all less than 3, indicating that the growth mode of LLM-105 in ethyl acetate as an anti-solvent crystal is a continuous growth mechanism, the nucleation rate increases as the supersaturation ratio increases, and the critical nucleus radius and the number of critical nucleation decrease as the supersaturation ratio increases.