The current indicator diagram sensing system of rod pumping well is not suitable for the pumping well at a low pumping speed, and the displacement accuracy is low. To overcome the shortcomings of the existing measuring equipment, an automatic indicator diagram sensing system with high precision displacement is designed. By analyzing a large amount of the data from the indicator diagram, it can be concluded that the motion trajectoriesof the polish rod are similar when the strokes are identical. An automatic acquisition method of high precision indicator diagram is proposed by using position sensing and displacement multiplexing, and the hardware composition and the key software of the sensing system are introduced in detail.Through analysis of the real data collected by the sensing system in the oil field, the results show that the sensing system is stable and reliable, and the lowest stroke can reach 02 times per minute.Moreover, the error of the stroke and the displacement is less than 1%. Compared with other types of indicator diagram sensing system, it has obvious advantages, and it completely satisfies the requirements of the indicator diagram acquisition system with widerange pumping speed and high precision for the oil field.