Different Trichogramma strains are differentiated from each other in biological characteristics, such as parasitic capability, which might be used for screening of superior Trichogramma strains. Here Inter-Simple Sequence Repeats (ISSR)-PCR was used to investigate the genetic variation of 7 candidate strains, and the molecular markers specific to different strains were subsequently identified. By optimizing the main parameters, the optimal ISSR-PCR reaction conditions for Trichogramma were firstly established. The results showed that the optimum concentrations of different reagents in a total of 20 μL volume were: 2.0 μL MgCl₂ (20 mmol/L), 1.6 μL dNTPs (.5 mmol/L each), 1 μL ISSR primer (10 μmmol/L), 1.5 μL genomic DNA and 0.4 μL Taq DNA polymerase (2.5 U/μL). The suitable PCR procedures were determined to be: pre-denaturing at 95℃ for 5 min, followed by 35 cycles of denaturing at 94℃ for 50 s, annealing at 52℃ for 1min and extension at 72℃ for 1 min 20 s, with a final extension at 72℃ for 10 min. Under the optimal conditions, the 7 Trichogramma strains tested could be discriminated by using ISSR-PCR. It is therefore suggested that this technique is helpful in identification and screening of Trichogramma strains.