Profiles development of the melt spinning process of poly(trimethylene terephthalate) (PTT) was simulated by a numerical method. The spinning speed of 3 km/min to 5 km/min was analyzed and the characteristic of PIT spinning process was compared with that of poly(ethylene terephthalate) (PET). Velocity development of PTT was slower than that of PET. Although PTT#s spinning temperature was lower than PET#s, the PTT solidified slower because of a smaller super-cooling and the large specific heat capacity. The diameter profile of PTT decreases gradually in comparison with that of PET. PTT#s strain rate has a broader distribution than PET#s and its maximum ranged from 541 to $570;s^{-1}$ for PET and 136 to $149;s^{-1}$ for PTT. PTT#s tensile stress was smaller than PET#s.