The molding molds for multi-layer composite transparent inserts of automotive interior parts need to meet requirements such as light transmittance, complex cavity structure, and high reliability, posing severe challenges to surface precision and greenization level in their manufacturing process. Traditional processing technologies have problems such as high energy consumption, heavy pollution, and difficulty in adapting to complex structures, which cannot meet the manufacturing needs of such molds. Focusing on the greenization of the entire mold processing process, this paper explores the optimization paths of key technologies including high-efficiency cutting, low-temperature nitriding heat treatment, and abrasive water jet polishing (AWJP). It studies the process parameters and experimental devices of AWJP for polishing complex inner cavities of transparent molds. The experimental results show that the surface roughness of the mold first decreases and then increases with the increase of jet pressure, with an optimal pressure range. The polishing effect is the best when the polishing time is 60–90 min and the jet angle is around 45°. Different abrasive grain sizes have significant impacts on the polishing effect: W5 abrasive can achieve lower roughness but with lower efficiency, while W12 abrasive has a higher removal rate but slightly higher roughness. With 2–30 MPa jet pressure and W12-W5 diamond abrasives as core parameters, high-precision finishing of complex cavity surfaces can be achieved through the flexible impact and grinding effect of gas-liquid-solid three-phase flow.