The invention discloses a testing apparatus for a surface temperature of a high-power diesel engine and a testing method thereof. The testing apparatus comprises an infrared thermal-image core for collecting surface temperature data information of a diesel engine. The infrared thermal-image core transmits detected temperature information to a data acquisition card in real time; and the data acquisition card transmits the received temperature information to a PC machine in real time. The PC machine is connected with a display unit, a network router, and a high-capacity hard disk; the network router is connected with a remote server; and the high-capacity hard disk is connected with a high-performance work station. According to the testing apparatus, the infrared thermal-image machine detects the surface temperature information of the high-power diesel engine in real time and transmits the detected temperature information to the PC machine in real time; and then the information is transmitted to the display unit for data displaying. And the temperature information is displayed at a temperature display interface based on labview programming and a temperature cloud atlas having a temperature contour line is displayed simultaneously.