【Aim】 The casuarina moth, Lymantria xylina, is one of the main pests of Casuarina equisetifolia, in the coastal areas of Fujian Province. It has the potential to become an international quarantine pest. L. xylina multiple nucleopolyhedrovirus (LyxyMNPV) is an excellent resource for the control of L. xylina as it is a natural enemy of this pest and is very safe for use in the environment. The establishment of PCR detection for LyxyMNPV is conducive to the study and control of L. xylina. 【Method】 A pair of specific primers was designed according to the previously reported unique gene gp131 of LyxyMNPV. The target gene fragment was amplified using PCR and sequenced to establish a rapid PCR detection system. 【Result】 The detection limit of our method was 1 fg·mL^-1 for LyxyMNPV DNA or 5.0 PIB·mL^-1 for polyhedrons. It had high specificity in distinguishing LyxyMNPV from the other seven insect nucleopolyhedroviruses, and was detectable in different developmental stages of infected L. xylina, including eggs, larvae, pupae, and adults. This system has also been successfully used for virus detection in the soil, host plant branches, and parasitic wasps of L. xylina. 【Conclusion】 A highly specific and sensitive molecular rapid PCR detection method was successfully established, which provided convincing and microscopic molecular evidence for the rapid detection of LyxyMNPV.