Objective In order to determine precise adhesion strength of hard film, the effects of parameters of scratch test on the critical failure load were studied and discussed. Methods Titanium Nitride (TiN) film was deposited on 304 stainless steel plates and Si wafer by magnetron sputtering. The cross-section morphology and thickness of TiN film were observed by Scanning Electric Microscopy (SEM), the hardness was evaluated by nano-indentation method, the adhesion strength was studied by scratch tester, and the influences of slide length, slide speed and loading rate on the critical load were analyzed. Results As-deposited TiN film possessed dense morphology with a thickness of about 2 μm. The hardness of TiN film was about 2300HV and the TiN/304 stainless steel system was hard film and soft substrate. The increase of slide speed (1 ~3 mm/ min) resulted in the first acoustic emission (AE) signal delay under the same load (10 N) and slide length (3 mm) conditions, the increase of slide length (3 ~ 9 mm) resulted in the gradual weakening of III and IV failure mode under the same load (10 N) and slide speed(3 mm / min) conditions. Conclusion In order to evaluate ideal adhesion strength, I to IV failure mode appearance should be observed in single scratch path with specific AE signal. Critical load repeated itself within proper range of testing parameters. Position 4. 9 N AE signal appeared during several tests under different setting parameters, in combination with the scratch morphology, it clarified that the adhesion strength of as-deposited TiN film was 4. 9 N.