The utility model discloses an electromagnetic ultrasonic sensor which comprises an electromagnet (101), an emitting and receiving coil (100) and a measured metal (102), wherein the electromagnet (101) is adhered to the emitting and receiving coil (100); the emitting and receiving coil (100) is placed on the measured metal (102); an excitation power supply (103) of the electromagnetic ultrasonic sensor comprises a signal generation circuit (200), a pulse string control circuit (201), a power amplification circuit (202) and an impedance matching circuit (203) which are sequentially connected with one another; and the output of the impedance matching circuit (203) is connected with an emitting coil. The electromagnetic ultrasonic sensor has the advantages that the number of pulse strings, the frequency and the phase of an excitation signal generated by the excitation power supply can be adjusted according to different conditions of the metal to be measured; and the emitting power is maximized through the impedance matching circuit, so that the electromagnetic ultrasonic conversion efficiency of the electromagnetic ultrasonic sensor can be maximized.