Abstract: In this work, a twocavity single parting surface injection mould was designed by a combination of the characteristics of plastic parts.A type of complex structural demoulding mechanism with half slide blocks was designed with regard to the demoulding difficulty of plastic parts.In this complex mechanism, the entire circumference surface of the outer wall was demolded in a side core pulling mode by two half slide blocks in the main mechanism body.The left slide block of the half slide blocks was used to drive the core pulling and demoulding mechanisms of the inner core, and the right slide block was used to drive the lateral inclined top coring mechanism installed in the body of the right slide block to perform the upper side demodulation of the inner wall.This design for the complex demoulding mechanism with half slide blocks is fairly reasonable.Especially for the two submechanisms driven by the left and right sliders, the wellconceived design could effectively utilize the motion power of the half slider mechanism to perform a secondary drive, which led to a smart demodulation for the plastic parts with local complex features.The design of the mould release mechanism was simplified, thus leading to a decrease in difficulty of mould design.With a reasonable mould structure and reasonable and reliable mechanism layout, the mould designed in this work could be taken as a good reference for the design of similar moulds.