According to the complicated gas-liquid flow in liquid-ring pump, the large amount of calculation, and the difficulty for its optimization design, the flow field reconstitution for the gas-liquid flow of liquid-ring pump based on proper orthogonal decomposition were proposed. The blade was parameterized by Taylor polynomial, and the experiment samples can be designed by introducing small perturbation of the control parameter. The transient gas-liquid flow in liquidring pump was simulated by using the VOF model. The snapshot set consisted of the control parameter for the blade shape and the flow field data. According to the geometric similarity of the impeller flow passage and the mesh deformation technology, the flow field data of the similar position of each point were interpolated. The snapshot set can be decomposed as linear combination of orthogonal basis by using proper orthogonal decomposition. The coefficients of the objective blade orthogonal basis were fitted by the least square method. The flow field data of the objective blade were reconstructed. In the calculation case for the type of 2BE-203 liquid-ring pump, the gas-liquid flows of single blade passage were reconstructed, and almost all the flow structures were accurately predicted. The prediction had high accuracy except near the gas-liquid interface. The calculation amount for the multiphase flow field was greatly reduced.