Abstract: Various studies on thedevelopment of boundary layer in turbomachinery were summarized.Periodic upstream wakes can change the transitional mode, anddominate the strong unsteadiness of BL flow. Different turbulenceintensities and frequencies of upstream wakes can generatedifferent S-T diagram of BL, and furthermore, the unsteady effectof wakes on BL can be influenced by Reynolds number, profileloading, surface roughness, inlet condition etc. And then,mechanism of the wakes'effect was analyzed, and the development oftransition model was presented. Finally, two question about theboundary layer research, which should be paid attention to in thefuture, were pointed out as well as some works about vorticesmovement in BL separated flows.