The cyclone is widely used to separate ash or dust from two gas-solid or liquid-solid flows in the industrial process. The velocity distribution in cyclone separators is important for predicting the cut-size and efficiency of particles and pressure drop in cyclones. Although there are a lot of experimental results in the references for velocity distributions in cyclones, these cyclones in experiments tend to be smaller compared with the actual cyclones. In addition, the simulating results of velocity distribution for cyclones also cost a lot of computational time. In this paper, based on Ogawa's simplified model, the dimensionless equations are derived to predict the tangential velocity distribution in cyclone separators; based on Ingham's model, the dimensionless equations are derived to predict the axial velocity distribution in cyclone separators. To verify the accuracy of the dimensionless velocity model, the predicting results are validated with the test data from four different cyclone separators. Compared with the experimental results, the tangential velocity model fits well in both the quasi-free vortex region and the quasi-forced vortex region, and the axial velocity model fits well in the quasi-free vortex region. The models are expected to provide a relatively accurate prediction of the separating behavior of large cyclones, which will be of benefit to the design of industrial large cyclones.