An accurate detection of the effective values of electric voltage and current from high frequency power generators is a precondition for the development of smart electrotomes. In this light, an energy detection system based on personal computer (PC) is developed hereby. It senses voltage and current in isolation from generators with transformers, and then the measured values are amplified, filtered, transformed into single-ended signals and converted to RMS. The detected signals are transformed into digital signals through Data Acquisition Card (DAQ) and the data are processed with quadratic fit in Labview. Finally, the controller completes constant power output. The experiment results indicate that the energy detection system can measure the output parameters precisely and the controller can achieve constant power control.