The SiO2 thin film was deposited on the PET surface through magnetron sputtering technology, the coating surface morphology was observed by scanning electron microscope (SEM), and the adhesion strength of SiO2/PET coating-substrate system was detected by adhesion strength tester. The effect of PET substrate cleaning process on the adhesion strength of SiO2/PET coating-substrate system was investigated. The results showed that the adhesion strength of coating-substrate system after plasma cleaning was maximum, up to 0.14 MPa, and increased by 7.83%, 27.27% and 55.56% comparing with that of the deep cleaning, general cleaning and no cleaning, respectively. The plasma cleaning process parameters played an important role in the adhesion strength of coating-substrate system, and the adhesion strength firstly increases and then decreases with the increase of cleaning time, cleaning power and argon flow.