[Objectives]  To determine the effect of post-diapause photoperiod on the biological characteristics of Clanis bilineata tsingtauica Mell. [Methods]  Mature larvae were induced to diapause early and randomly assigned to one of four photoperiod treatment groups (L0∶D24、L8∶D16, L12∶D12 and L16∶D8). Several biological characteristics of each treatment group were then measured and compared. [Results]  Post-diapause photoperiod affected different biological characteristics of C. bilineata tsingtauica to different degrees. Exposure to longer day-length significantly reduced the pupation rate, the duration of the diapause and pupal stage and the oviposition rate (P<0.05). Longer day-length also tended to reduce pupal weight and pupal length. Photoperiod had, however, no significant effect on emergence rate or adult longevity.  [Conclusion]  A longer photoperiod of L16∶D8 reduced the pupation rate, pupal weight, oviposition rate, and the duration of the diapause and pupal stage of C. bilineata tsingtauica.