Abstract: In this paper, three models which are used to solve theω–field are discussed respectively. The model A is a multi-layer nonlinearω–diagnostic models, model B is a diabatic one and model C is a meso– scale one. They are applied to diagnose a mei-yu front heavy rain process. The differences from each other are analysed. The results show that the model C or model A is better for diagnosing the mesoscaleω field and the difference between twoω fields obtained from the two models is small. Model B is not generally used, but it can be used if the precision requirements are not high in order to save the calculation amount