Recently, low friction diamond like carbon (DLC) coatings are prevailed for engine parts improving the fuel efficiency of automobiles. The quality control for the adhesion strength of DLC coatings is very important because of higher internal stress in the film. In this paper, a new method to evaluate the adhesion by using a simple pin / disk sliding test with acoustic emission (AE) equipment are introduced. Not only for the determination of the delamination strength, but also for the estimation of the cause of delamination by analyzing the frequency profile of AE signals with FFT are attempted. As a result, we found that peaks in 350-600 kHz is a signal of delamination and peaks in 8 kHz /30 kHz are due to droplets on surface.