Antimony Selenide (Sb2Se3) is a promising candidate for thin-film solar cells; however, its low intrinsic doping density, which reduces its power convention efficiency, has limited its further application. In this study, the MoO3 thin films prepared by electron beam (EB) evaporation were used as the back contact layer in an Sb2Se3 thin-film solar cell to compensate for the low intrinsic doping density (insufficient carrier collection) of Sb2Se3 as well as to optimize the back contact issues of Sb2Se3 thin-film solar cell. To achieve this, solar cells with an FTO/CdS/Sb2Se3/MoO3 /Au structure were prepared. The thickness and deposition temperature of the MoO3 thin film were optimized, and the device achieved an efficiency of 6.3%, which was approximately 24% higher than that of the solar cells without MoO3. In addition, the material characterization revealed that the EB evaporation-prepared MoO3 thin film was amorphous and exhibited an n-type conductivity with a high work function and deep valence band edge, which facilitated the hole-selective transport. Furthermore, the device performance characterization and analysis revealed that the MoO3 thin film enhanced the efficient charge collection, improved the built-in voltage, and suppressed the carrier recombination at the back contact interface.