To evaluate the contribution of a built-in fin-type Trombe wall to reducing indoor heating energy consumption, this study takes a typical residential building in Lanzhou as the research object. Fins are installed on the heat-absorbing surface of the Trombe wall to enhance heat transfer and thereby improve the indoor thermal environment. The results show that the isosceles right-triangle fins with a height of 20 mm, a transverse spacing of 0.20 m, a longitudinal spacing of 0.533 m, and an in-line configuration provide the greatest improvement in heat transfer performance and indoor thermal conditions. Over the entire simulation period, the average Nusselt number (Nuˉ) of the fin-type Trombe wall is 21.28 higher than that of the finless wall. Compared with a conventional room, the energy-saving rates of the finless Trombe wall and fin-type Trombe wall rooms are 36.38% and 44.63% respectively, meaning the fin-type Trombe wall yields an additional 8.25% energy-saving improvement.