Abstract: Monochamus alternatus Hope is the major insect vector transmitting pinewood nematode disease, an important quarantine disease of pine forest. The virulence of a strain of Metarhizium anisopliae, MaYTTR-04, to adult M. alternatus was assayed by using the adult-conidial attaching method (attaching all tarsi of adult with dry conidial). The results showed that M. alternatus began to die at 6 days post inoculation (dpi) day at constant temperature (25℃±1℃, RH 70%±10%, light period 10L∶14D). The peak of death was between 18－21 dpi. The mortality of this beetle was 85% at 18 dpi when applied with the amount of inoculum at 2.3×10⁶±0.2×10⁶ spores/adult, and the LT₅₀ was 14.7 d. At room temperature (24℃－33℃, RH 40%－60%, natural light from north), the adult of M. alternatus began to die at 3 dpi. The peak of death was between 15－21 dpi. The mortality was 85% at 15 dpi and 100% at 21 dpi when applied with the amount of inoculum at 2.3×10⁶±0.2×10⁶ spores/adult, and the LT₅₀ was 12.9 d. When the adults of M. alternatus were kept in the cage in natural pine forest for 21 days, the average mortality of the adults dealt with conidia suspension was 60%, and the cadaver rate was 48.9%, while the average mortality of the adult deal with non-woven fabric strips of M. anisopliae was 86.7%, and the cadaver rate was 75.6%. It was concluded that this strain of M. anisopliae is high virulent to M. alternatus, and more virulent at higher temperature, which may serve as a productive strain of biocontrol agents and be used in forest for controlling M. alternatus.