Highly oriented magnetite (Fe3O4) thin films have been produced by reactive sputtering in a mixture of hydrogen and argon. While different phases can be achieved by varying the ratio between hydrogen and argon, single phase magnetite films can be achieved with hydrogen concentration γ=0.75%–1%. For the sample grown at γ=1.0%, a Verwey transition at about 111 K can be seen from the temperature dependence of the resistivity, which is confirmed in the magnetization measurements. Maximum magnetoresistance (MR) of about 13.8% is observed just about the Verwey transition at T=115 K. MR results also suggest strong coupling among Fe3O4 nanoparticles originated from the Ruderman-Kittel-Kasuya-Yosida exchange interaction and dipolar interaction, which requires high order terms of (M/Ms)2 to explain the MR behaviors. However, with the fields applied perpendicular to the plane, MR exhibits a distinct behavior. The MR values under the condition of low fields seem to show a linear relationship with |M/MS|.