In this talk a review on our recent work on fission theory from point of view of diffusion process is presented. The transient phenomena of fission rate are revealed and studied carefully. By comparison of the fission rate calculated both at the saddle and seission points, the latter is emphasized for actual calculation. Our investigation related to the enhancement of the neutron emission prior to fission induced by heavy ion reactions is reported. The quantum aspect of the diffusion model is studied, which is very important for low energy fission. Finally, the extension of one dimensional diffusion model to multi‐dimensional cases is also discussed.