Based on the mathematic model of single-phase voltage source inverter, an adaptive control method which can deal with unknown parameters and guarantee stable of the control system is systematically proposed in the paper. According to Lyapunov stability theory, an adaptive state observer is used to estimate variables adopted in the control law. Meanwhile, A 3rd order filter is used to deal with the original output reference voltage so that smooth and continuous output reference voltage as well as its differential coefficient are generated. The method guarantees the system stability and convergence of the output voltage tracking error. The theoretical analysis and experimental results verify the correctness of the method.