The high magnetoresistance is one of the most important properties that led the colossal magnetoresistance (CMR) materials been kept attention, however, because of the low phase transition temperature (Tp) and Curie temperature (TC) limits the application of the materials. The Tp could be influenced by many factors, as for the R1-xAxMnO3(R=rare earth element, A=alkaline metal, 0¡Õx¡Õ1) CMR materials, the selections of elements on R, A, and the ratio of x would make the difference. Besides these factors, when the film was grown on a substrate, the strain effect initiated at the substrate/film interface plays an essential role on the change of Tp and other physic properties. In other hand, the Sr element, existed in the SrTiO3(100) substrate, may also diffuse into the thin films during growth and alter the composition of the film and change its physic properties. In this thesis, we mainly focused on the modifying of the surface of substrates to prevent the diffusion problems. A wet chemical method was applied to modify the top layer of substrates such that the surface layer of the substrate is consisted of Ti-O layer only. By varying the high temperature annealing and etching processes, an optima processing condition was established.