In the middle and late stage of oilfield development, the water content of oil well continues to rise, and the water injection well is affected by factors such as sand production and well condition deterioration, so the difficulty of water injection is increasing, the cost of water injection is increasing, and the development benefit is gradually deteriorating. Some water injection Wells had to be shut down or diverted to production, resulting in a decrease in reservoir formation energy and a large number of low production and low energy Wells. These oil Wells have the production characteristics of "three low and one high and one difference", that is, low production, low energy, low efficiency, high production unit consumption and poor economic benefit. The working principle of the technology is as follows: a mathematical model is established in the data processing center (DSP) to calculate the position of the suspension point in real time, and the upper and lower dead points of the smooth rod are calculated automatically through the software based on the reference signal of each stroke of the smooth rod input by the external switch quantity, which is used as the basis for the variable speed operation. The technology realizes the independent closed-loop control of the motor's electric parameters such as speed, position, current, torque and voltage, and can realize the whole variable speed operation of the pumping unit according to the production needs of the oil well.