Polymorph predictor is a useful tool for crystal structure. Prediction with this method,the structure of triamino-trinitrobenezene (TATB) was simulated. Parameters of crystal structure were P-1,a=9.01Å,b=9.01Å，c=6.01Å,α=90.01°,β=120.00°，γ=90.01°,ρ=2.03 g·cm^-3,XRD spectrum was also obtained (there were strong absorbing peaks at 2θ=11.5°,29.5°) . The calcu lated results were very close to experimental results.