Al-Si-based alloys are commonly used for lightweight material design in the automotive industry. To meet the lightweight application requirements of fixed rotor parts of hydraulic retarders for heavy-duty vehicles, a novel Al-12Si- 3.5Cu-0.4Mg cast aluminium alloy was selected as the research object. The T6 heat treatment process of the experimental alloys and its effect on the dry friction performance were investigated. The microstructure of the as-cast experimental alloy is mainly composed of a primary α-Al phase, eutectic Si phase, and Al2Cuphase. After solution treatment, the eutectic Si phase is spheroidized, and the Al2Cuphase dissolves into the matrix. After aging treatment, a large amount of the nanosized θ′ phase is dispersed and precipitates in the matrix. The T6 heat treatment process for the as-cast experimental alloy was as follows: solution at 470 ℃ for 12 h and water cooling, followed by aging at 180 ℃ for 10 h and air cooling. After T6 heat treatment, the room temperature mechanical properties of the as-cast experimental alloy significantly improved, with the ultimate tensile strength and hardness increasing from 221 MPa and 92 HV in the as-cast state to 322 MPa and 144 HV, respectively. Moreover, the T6 heat treatment significantly improves the dry friction performance of the as-cast experimental alloy. The main reason is the high hardness of the T6 state experimental alloy, which makes it difficult for the abrasive particles generated by wear to press into the matrix and produce more oxides.