The invention provides a method for determining the critical rotating speed of a wet rotor of a multistage
centrifugal pump. According to the method, an automatic node division module, a model creating module and a model calculation module are mainly utilized for determining the critical rotating speed, and the
data processing is carried out among the modules in a sequence sequentially from the automatic node division module, the model creating module and the model calculation module. Firstly, the automatic node division module creates a geometrical model of a wet rotor
system on the basis of an
engineering drawing, and in addition, the automatic division of
modes is carried out; secondly, the model creating module is utilized for inputting physical parameters of parts such as rotating shafts, impellers, bearings and sealing clearances, and a total
mass matrix [M], a total
rigidity matrix [K], a total
damping matrix [C] and an overall calculation model of a multistage
centrifugal pump shaft
system are built; finally, the model calculation module is utilized for solving the overall calculation model of the multistage
centrifugal pump shaft
system, a Campbell chart is drawn, and the required first n step of critical rotating speed is obtained. The method has the advantages that the operation is simple, the
engineering applicability is wide, the critical rotating speed of the wet rotor of the multistage centrifugal pump can be calculated under the condition of different structures, the
engineering design and the application of the rotor of the multistage centrifugal pump are guided, the design period is shortened, and the production efficiency of the rotor of the multistage centrifugal pump is improved.