Abstract: B eauveria bassiana spore suspension wasmixed with trehalose, glucose, L-alanine and FeSO4 respectively,and were made up 4 different concentrations of synergist of B. bassiana spore suspension, then inoculated them on theM onocham us alternatus larvae. The results showed that four different kinds of synergistsmade a certain synergism inthe p rocess of control of B. bassiana toM. alternatus larvae. The death rate ofM. alternatus larvae was increased onan average of 18. 05% by trehalose-additives; That was increased on an average of 8. 75% by glucose. In the 11thday, the death rates of M. alternatus larvae were increased on 23. 1%, 76. 9%, 15. 4%, 53. 8% respectively bydifferent concentration spore suspensions of trehalose. They were increased by 30. 8%, 0. 0%, 53. 8%, 7. 7%respectively by glucose, increased by 38. 5%, 23. 1%, 23. 1%, - 7. 7% respectively by L-alanine, and increased by14. 04%, 36. 39%, 16. 71%, 20. 67% respectively by FeSO4.