Abstract: To focus ultrasonic energy by using electromagnetic ultrasonic phased array technology in a buried steel pipeline, and improve detection accuracy on the pipe wall, this paper presented a method of high frequency and high power multi-channel exciting source based on radio frenquency (RF) theory and class-DE power amplifier technology. Multi-channel pulse sequence of time sequence and phase delay was realized by using filed-programmalbe gate array (FPGA) and digital delay method. High frequency "floating gate" problem of the exciting source was effectively solved by optical fiber isolated pulse signal and power isolation transformed reference potential. Based on operating characteristics of the class-DE switch tube and power amplifying circuit, a class-DE power amplifier simulation model was established by using Pspice software. Experimental data shows that when it is working in the operation frequency of 1.1 MHz and voltage of 300 V, the design of exciting source can output 1 ns delay pulse sequence, the output power of electromagnetic ultrasonic array element is 1.5 kW, and I_p-p is 20 A of alternating current, which meet the requirements of inspection technology of electromagnetic ultrasonic phased array.