The invention discloses a system and method for self-adaptive identification of piano key action. The system mainly comprises a key detection unit and a main control unit. The method comprises the steps of 1, applying for an array BOT [7]; 2, initializing peripheral equipment; 3, scanning the ADC value once; 4, gradually switching on all LEDs and then switching off the LEDs to show that equipment is ready, and to prevent the situation that the IO state of the equipment is unstable during starting to make the LEDs switched on by accident; 5, making the equipment enter the working state; 6, scanning the ADC value of seven white keys circularly; and 7, sending a key press-down signal through UART if the ADC value is larger than the rising threshold VH[i], sending a key lifting signal if the ADC value is smaller than the descending threshold VL[i], and returning to step 5 for the next round of scanning. A hysteresis comparative method is adopted, one third and two thirds of the difference value of output voltage of a phototube reflected by a lifted key and a pressed key are used as comparative values, false triggering is effectively avoided, accuracy is high, stability and reliability are realized, and using is convenient.