This experiment was conducted in June, 2015 and March, 2016, in a Pine forest field situated in Xuan Chen City in South-Eastern China to evaluate the efficacy of the entomopathogenic fungus (Beauveria bassiana strain Bb13) in combination with deltamethrin in different formulations to control the Masson pine caterpillar (Dendrolimus punctatus). Total corrected mortality rate of Masson pine caterpillars was significantly higher in combined formulations compared with B.bassaina oil formulation. In 2015, the corrected mortality in the combined treatments ranged between 49.6 to 99.8%, and 28.5% corrected mortality was recorded for the B.bassiana oil formulation. While the maximum corrected mortality of 99.8% and (4.6%) fungal infection was observed in the treatment 6000 ml oil formulation 12,000 µl deltamethrin, the maximum corrected fungal infection (12.2%) was observed in B.bassaina oil formulation. And a mortality rate of 7.1% was observed in control. In 2016, a corrected mortality range from 77.1 to 100% was observed in the combined formulations. The treatment 3000 ml oil formulation 3000µl deltamethrin showed a final corrected mortality of 95.4% with the maximum fungal infection rate of (62.5%), the lowest corrected mortality (33.0%) was observed in B. bassiana oil formulation at the end of experiment. Mortality of 11.1% was observed in the control.