There are limited quantitative studies of the effectiveness of China' s fiscal policy. Comparatively, overseas studies dig deeper on the same topic. In this paper, a VAR(Vector autoregression) model is used to analyze the effectiveness of China's fiscal policy. Four variables are selected in the VAR model: household consumption , private investment,exports and imports. The papers intends to make a breakthrough in the quantitative analysis of the effectiveness of China's fiscal policy , especially from an angle of operating mechanism.