The invention provides an engine air inlet freezing detection system. An air inlet of an engine is covered with a filter cover, and the inherent frequency of the filter cover is larger than or equal to the vibration frequency of the engine when the engine is at idle but smaller than or equal to 150% of the vibration frequency of the engine when the engine is at 100% rotating speed. A detection device is used for detecting the vibration state of the filter cover; a control device is in signal connection with the detection device and obtains state information of the filter cover according to vibration state signals detected by the detection device. According to the engine air inlet freezing detection system, when the filter cover is frozen, due to the weight change, the vibration frequency is reduced to be equal to the vibration frequency of the engine, resonance is generated, the detection device can detect the vibration state and change of the filter cover, the control device can obtain the state information of the filter cover according to the detected vibration state change, and the freezing phenomenon of the filter cover is found in time.