Pattern recognition receptors are known to participate in the activation of Prophenoloxidase system. In this study, a 1,3-${eta}$-D-glucan recognition protein was detected for the first time in Antheraea pernyi larvae (Ap-${eta}GRP$). Ap-${eta}GRP$ was purified to 99.9% homogeneity from the hemolymph using traditional chromatographic methods. Ap-${eta}GRP$ specifically bind 1,3-${eta}$-D-glucan and yeast, but not E. coli or M. luteus. The 1,3-${eta}$-D-glucan dependent phenoloxidase (PO) activity of the hemolymph inhibited by anti-Ap-${eta}GRP$ antibody could be recovered by addition of purified Ap-${eta}GRP$. These results demonstrate that Ap-${eta}GRP$ acts as a biosensor of 1,3-${eta}$-Dglucan to trigger the Prophenoloxidase system. A trace mount of 1,3-${eta}$-D-glucan or Ap-${eta}GRP$ alone was unable to trigger the proPO system, but they both did. Ap-${eta}GRP$ was specifically degraded following the activation of proPO with 1,3-${eta}$-Dglucan. These results indicate the variation in the amount of Ap-${eta}GRP$ after specific immune challenge in A. pernyi hemolymph is an important regulation mechanism to immune response.