The voltage stability control of off grid microgrid is the key and core issue of power grid stability. Aiming at the problem of voltage stability control of off grid microgrid with unbalanced nodes, the Newton Raphson homotopy algorithm is proposed to calculate the power flow, estimate the reactive power margin of each load node, and adopt reactive power supply droop compensation control for weak nodes to improve the voltage stability level. The simulation verifies the effectiveness of this method.