The YMnO3/TiO2 composite photocatalysts with high photocatalytic activity for the degradation of tetracycline hydrochloride have been synthesized successfully via a simple cryogenic route. The characterization of phase composition, purity and functional group information showed that YMnO3 and TiO2 were the main components of YMnO3/TiO2 composite photocatalysts. After the coupling of YMnO3 and TiO2, the average particle size decreased compared with YMnO3, but increased compared with TiO2. With the increase of YMnO3 content, the ultraviolet–visible (UV) absorption coefficient of YMnO3/TiO2 composite photocatalysts decreases, while the visible optical absorption coefficient increases. The photocatalytic activity of YMnO3/TiO2 composite photocatalysts also increased with the increasing of YMnO3 content. The capture experiment and photocatalysis mechanism analysis showed that the holes, hydroxyl radicals and superoxide radicals played an important role in the photocatalyst degradation of tetracycline hydrochloride under simulated solar irradiation by YMnO3/TiO2 composite photocatalysts. This simple synthesis technique will provide technical reference for the construction of other type I band arrangement heterojunction photocatalysts.