The sensitive core flow sensor is based on the heat transfer principle. The sensor structure consists of a microheat source located on the sensitive film, an upstream temperature sensor and a downstream temperature sensor symmetrical to the microheat source, and an ambient temperature sensor located on the silicon base. When there is no fluid flow on the sensor surface, the temperature field around the microheat source is symmetrically distributed, as in (a); when there is fluid flow on the sensor surface, the temperature field around the microheat source is disturbed due to the cooling effect of the fluid on the microheat source, and the upstream and downstream of the microheat source is asymmetrically distributed, as in Fig. (b); the greater the velocity of fluid flow, the greater the flow rate of gas carried away from the microheat source, and the asymmetry is greater. The flow velocity of the fluid is obtained by the temperature difference between the upstream and downstream temperature sensors.