Abstract: In the study,the changes of particle size distribution,zeta potential,rheological properties,emulsifying activity and emulsion stability of soymilk system under alkaline protease biological dissociation at 0,10,20 and 30 min were studied. The stability of the soymilk system was investigated by multiple light scattering stability analysis. The research results showed that when the biological dissociation was 20 minutes,the average particle size of the soymilk system was 456 nm,and the particle size of the soymilk was mainly distributed in 100~1000 nm. With the increase of the biological dissociation time,the particle size distribution was more concentrated and the averoge particle size decreased continuously. When the biological dissociation time was 30 minutes,the maximum absolute value of the potential was 30.3 mV. As the dissociation time increased,the emulsification activity and emulsification stability decreased to certain extent. Biological dissociation did not change the fluid properties of soymilk. Multiple light scattering analysis showed that the particle size of the soymilk system was more uniform and stable. In conclusion,biological dissociation technology can be used as a means to improve the stability of the soymilk system.