Abstract: Aiming at the existing problem of high-voltage flameproof switch in realizing integrated protection, namely under influence of disturbance of decaying DC component,decaying DC component can not be filtered by traditional full wave Fourier algorithm,so that the protection will easily fail to operate or unwanted operate. The paper presented an improved full wave Fourier algorithm which could filter completely decaying DC component and higher order harmonic signal. It also gave hardware structure of high-voltage flameproof switch based on the algorithm. The experiment proved this algorithmis is reliable and accurate and has a little calculated amount, and is a feasible method for intelligent high-voltage integrated protection.