The capacitors’ voltages could be unbalanced and unstable at the dc link in the cascaded multilevel static synchronous compensator(STATCOM). A strategy that the rectifiers control the capacitors’ voltages is presented. The modelling of the system and the design process of the controllers are listed. Also the system’s model is built on the simulation software SIMPLORER .The result of the simulation shows that the rectifiers could efficiently compensate the power loss difference in the H bridges, which keeps the capacitors’ voltages in benign balance and stability. The result also gives the comparison when the inverter works under the direct current control and the indirect current control ,in which the advantages and the disadvantages are discussed. The strategy suggested is practical and feasible.