The effects of oxygen vacancies and strain on the magnetism and Curie temperature of La_0.7Sr_0.3MnO₃ (LSMO) thin films deposited by PLD are investigated by changing oxygen partial pressure and increasing the interface mismatch between LSMO and SrTiO₃. The presence of oxygen vacancies reduces the double exchange effect between Mn³⁺ and Mn⁴⁺ ions, and the high-quality crystals effectively increase the Curie temperature of LSMO. Moreover, SrTiO₃ simultaneously exerts strain on the upper and lower interfaces of the LSMO film to promote orbital reconstruction of the e_g electrons in the Mn³⁺ ions. These electrons preferentially occupy the e_g(x²-y²) orbit and lead to an enhancement in the in-plane ferromagnetic exchange effect, thereby increasing the Curie temperature. These results suggest that the magnetic properties of these materials can be controlled through artificial structure design and provide guidance for their application in high Curie temperature spintronic devices.