The invention discloses a method for monitoring abrasion loss of an impeller wear ring of a multi-stage centrifugal pump based on the computational fluid dynamics theory. The method comprises the following steps: 1) modeling a flow field of the complete set of the multi-stage centrifugal pump on the basis of the complete flow field modeling analyzing part of the computational fluid dynamics theory, and calculating the efficiency of the multi-stage centrifugal pump under different wear ring gap size, so as to obtain a curve that the efficiency varies based on the abrasion loss of the wear ring; 2) monitoring the efficiency of the multi-stage centrifugal pump in real time, correspondingly reading pressure and flow data from inlet and outlet pressure transmitters and flow transmitter of the multi-stage centrifugal pump, and reading the motor efficiency and power factors, so as to achieve real-time monitoring of the efficiency of the multi-stage centrifugal pump; 3) acquiring axial and radial vibrating signals, and measuring the radial vibration number of a rotor; 4) determining whether the efficiency is reduced due to the abrasion loss of the wear ring according to the acquired axial and radial vibration signals, and presuming the abrasion loss of the wear ring according to the calculated real-time efficiency and efficiency relationship curve of the multi-stage centrifugal pump.