The main purpose of this paper is to analyze the characteristics of the flow field in fan rotor. Nowadays the twisted and swept fan is the representative work of the forefront of aerospace engines. The tip clearance flow field can have a large impact on fan rotor performance. This article describes and uses the throttle method to obtain near stall condition. Near stall condition value simulation of the transonic fan rotor was carried out by CFX. The Proper Orthogonal Decomposition method was applied to the tip flow-field analysis. The main structure of the flow field can be distinguished by Proper Orthogonal Decomposition method. Then the flow structure is sorted according to energy. Disturbing fine flow structures can also be captured. This provides a comparative reference for flow field visualization. It also provides important data for the design of the fan.