A finite control set model predictive control strategy based on the improved virtual space vector (IVSV-FCSMPC) was proposed for DC side midpoint potential imbalance problem of midpoint-clamped three-level rectifiers. Firstly, based on multi-vector synthesis and the characteristic that virtual space vectors do not cause midpoint potential fluctuations,a single-objective value function based on current tracking control was constructed to achieve unweighted coefficient based predictive control. Secondly, a dynamic adjustment factor based on midpoint potential feedback was designed to adjust the action time of positive and negative small vectors and medium vectors in the vector synthesis process. Two pairs of redundant small vectors were simultaneously adjusted within the small sector range of the low modulation regime. In the small sector range of the high modulation regime without redundant vector action, the virtual space vector switch sequence was optimized by improving the virtual medium vector to suppress midpoint potential fluctuations, achieving precise control of midpoint potential balance within the full modulation regime range. Finally, the experimental verification was carried out based on the hardware platform of the three-level rectifier. Results show that the designed control method has good current tracking control performance, excellent midpoint potential balance control and fast response speed.