The invention discloses an automatic hot riveting device for a sensor and a hot riveting method for the automatic hot riveting device. The automatic hot riveting device comprises a base, an air cylinder, a hot riveting rod, a pre-pressing pole and a sensor positioning block, wherein the sensor positioning bloc is arranged on the base; the air cylinder is arranged on the base and is located above the sensor positioning block; the hot riveting rod and the pre-pressing pole are arranged on a piston rod; and a heater is arranged in the hot riveting rod. The hot riveting method comprises the following steps: starting equipment, and waiting to heat the hot riveting rod to a set temperature; putting the sensor on the sensor positioning block; enabling the hot riveting rod to move downwards, descending above a plastic fixing post of the sensor and stopping; preheating the hot riveting rod, and pressing the hot riveting rod until the top of the plastic fixing post is shaped; and enabling the hot riveting rod to move and reset upwards, and taking out the riveted sensor. The production efficiency is improved; the cost is reduced; the product quality uniformity is good; and the product quality is convenient to control.