Indium doped ZnS (ZnS:In) films were prepared on glass substrate using thermal evaporation technology. It was found that the structural, optical and electrical properties of ZnS:In films strongly depend on the substrate temperature (T_s). By X-ray diffraction (XRD), atomic force microscopy (AFM), transmittance spectroscopy, and electric performance measurements, the effect of T_s on ZnS:In film is studied in detail. It reveals that T_s has important effect on ZnS grain size, crystallinity, lattice disorder, etc., which further leads to the obvious influence on its optical and electrical performance. Under the optimized T_s, the performance, especially the conductivity, achieved in this work is far higher than that reported for other n-type ZnS films.