In order to predict the temperature distribution of the cavity surface of the injection mold under the given cooling channel distribution, the temperature analysis of the injection mold is carried out by the boundary element method. For the temperature field problem of injection mold, the boundary element method has the advantages of small data preparation, small calculation amount and high precision. However, since the cavity inside the injection mold is a slit and the length of the cooling hole is much larger than its diameter, the ordinary boundary element method cannot be calculated. According to the structural characteristics of the injection mold, the boundary integral equation suitable for the cooling analysis of the injection mold is derived, and the boundary element calculation method of the three-dimensional temperature field of the mold is given. Practice shows that this software has a good guiding effect on the analysis and design of injection mold cooling system.