Abstract: Aspheric surfaces are widely used in optical systems. Aspheric surface parameters, including vertex radius of curvature, conic constant, and high-order aspheric coefficients participate in optical design, manufacture, measurement, alignment and assembly. Precision measurement for aspheric surface parameters is the basis for manufacture, alignment and assembly. A partial compensation measurement system is proposed based on virtual-real combination interferometer for aspheric surface parameter error measurement. In this measurement system, residual wavefronts are measured by partial compensation interferometry. The interferometer is multiplexed in cat-eye-wavefront positioning method to measure the compensation distance which is the distance between compensator and aspheric surface under test. Aspheric surface parameter errors are calculated by virtual-real combination iterative algorithm. The system only needs to introduce a converging lens into the optical path of partial compensation interferometry, which is easy to align and assemble, and has high measurement accuracy. The effectiveness and accuracy are verified through the measurement of a 4th-order aspheric surface.