All of the photoelectric detectors under laser irradiation are likely to be damaged, which has a bad effect on the detector performance. In order to study the photodiode damage caused by the multi-pulsed laser irradiation, a two-dimensional axisymmetric model and a heat source model of the photodiode irradiated by the multi-pulsed laser are built. Temperature distribution of the photodiode irradiated by the 1064 nm millisecond multi-pulsed laser is simulated by the finite element software COMSOL Multiphysics. Results show that when the pulse number N of the multi-pulsed laser irradiation is 1, 3, 5, 10, 30, respectively, pulse energy density region required by the fusion damage threshold of the photodiode is 19.1-76.4 J/cm2. The research results are helpful for the millisecond multi-pulsed laser in laser processing and the application of laser protection.