The traditional sampling system is not able to collect the energy of point target effectively,which leads to low SNR of the image and small image spot.To solve these problems,the bidirectional over-sampling system was used to detect weak point target.The model of point target sampling system was built,and the detecting ability of bidirectional over-sampling system for point target was analyzed.According to the model of point target sampling system,the distribution of the obtained point target on the image is uniform,the gray gradient is small,and point target has a certain area.The energy distribution of the target obtained by the sampling model shows that the bidirectional over-sampling system is able to collect the energy of point target effectively,the SNR is stable,and the area of target is larger.The sampling system has strong adaptability to the relative position of the point target.The simulation result shows that detection method can effectively improve the SNR of the point target image.