To the photo-solidification rapid prototyping technology, the precision of parts relate directly to their size and structural characteristics, not to their complexity. However, variant prototyping processes bring about variant surface shapes and dimension precisions. The authors compare its prototyping precision and prototyping time by testing a thin-shell exterior trimming part at variant laying angles and under variant bracing conditions. And then reduced model is founded, warping deformation of variant bracing diaphragms and sheet metals at optima laying angle are surveyed, finally the process to upraise the rapid prototyping precision of the thin shell parts is set up. Experiments are then done to test the process.