By using a pulsed low energy positron lifetime system

the positron lifetime spectra were measured of the high- temperature superconducting epitaxial thin film YBa2Cu3O7-x samples prepared by the pulsed laser deposition （PLD）

magnetron- sputtering method and evaporation method

respectively. It is found that besides shallow positron trapping centers there ace a number of deep trapping centers which the bulk material lacks. At low temperature the deep trapping centers have a tendency to enlarge. The relationship between positron lifetime and the deposition conditions （substrate temperature and partial air pressure） of the PLD films indicates that the defect type is independent of the deposition conditions and the defect concentration increases with decreasing substrate temperature or rising partial air pressure.