Cooling analysis in injection molding finally solves the BEM equations of mold surface temperature.There are many integral items in these equations.Because they can hardly be expressed in analytical form，so we cannot get their accurate analytical solution.Instead，we get their numerical solution with the Gauss integration method.To some extent，its precision is low.This paper adopted approximate-analytical solution and semi-analytical solution instead of numerical solution.In this way，the integral precision on some key points was enhanced by more than 10%.Furthermore，the accuracy of cooling analysis and the condition of the BEM equations were improved effectively.