Pr0.5Ca0.5MnO3(PCMO) is been prepared by a solid-state reaction technique, and the thin film of PCMO is deposited on an n-type silicon substrate by a pulsed laser deposition method. Experimental results indicate the transport character of the film may be consistent with the variable range hopping model in a temperature range of 80—300 K, but it changes from one-dimension to two-dimensional and then turns three-dimensional with temperature increasing. It may be attributed to the effect of orbit order on the transport characteristics. The PCMO/Si heterojunction possesses good rectifieation property under a magnetic field,and at a positive voltage the heterojunction shows its magnetoresistance to have a remarkable transition from positive to negative.