With the case of a vehicle-used high-gloss blue-tooth part,the influence of mold temperature in rapid heat cycle molding(RHCM) on sink marks of plastic part was investigated based on numerical simulation technology.This thesis also studied on other parameters impact on sink index of part with fixed or changed mold temperature condition.The results reveal that the sink index of RHCM part is less than of conventional part distinctly at the same process conditions,and it decreases as quasi-linear with mold temperature increases gradually.Under the same mold temperature conditions,the packing pressure is the most significant parameter on sink index of part,melt temperature,the injecting pressure and packing time are almost same effect on it,while the cooling time has have the no impact on it.With gradually elevating of mold temperature,the sink index of part shows a modest decrease under the same melt temperature and injecting pressure conditions.While it fluctuates as a "V" shape in small range under the same packing pressure,packing time and cooling time presumed conditions,and reaches the minimum near the thermal deformation temperature of plastic.