Abstract: Taking the vertical diffuser of Silaogou Coal Mine in Shanxi Province as a reference, the model test of diffuser was carried out to study the influence of elbow guide vane structure on the diffusion efficiency of diffuser. In order to solve the problem of excessive resistance at the elbow of the original device, a new elbow device equipped with guide vanes was designed. The test results show that recovery dynamic pressure efficiency of diffuser with guide vanes at new elbow is significantly improved compared with that with original elbow. The research results play a guiding role on the efficient operation of mine main fan.