The invention discloses a drowning lifesaving device based on pyroelectric infrared sensing and a using method. The drowning lifesaving device is characterized in that a life buoy is clamped at the front end of a clamping frame of the drowning lifesaving device, a main propelling motor and a main propeller are arranged at the tail end of the clamping frame, a pyroelectric human body infrared sensor is arranged at the end surface of the main propeller, an auxiliary propelling motor and an auxiliary propeller are arranged on one side of the rear portion of the clamping frame, a controller is arranged at the rear portion of the clamping frame and electrically connected with the main propelling motor, the auxiliary propelling motor and the pyroelectric human body infrared sensor, and a storagebattery is arranged in the controller and provides a working power supply of the drowning lifesaving device. The using method comprises the following steps that the auxiliary propeller makes the clamping frame rotate integrally, and the pyroelectric human body infrared sensor searches for a drowning to-be-rescued person; when an infrared signal radiated by a body of the drowning to-be-rescued person is sensed, the auxiliary propeller stops, the main propeller drives the clamping frame to get close to the drowning to-be-rescued person, after the clamping frame is close to the drowning to-be-rescued person, the life buoy is taken down to sleeve the body, so that drowning rescue is completed. According to the device and the method, automatic searching and the operation of quickly getting close to the to-be-rescued person are realized, and the rescue efficiency is improved.