Based on the market requirements and legislations for brakes of heavy duty vehicles, several kinds of common supplemental brake devices were compared and the engine compression release brake was finally determined as the development reference. One supplemental brake system for 10 L/20 L engine was developed in accordance with the market requirements and the compression release brake system was introduced in detail from the aspects of project design and test process. The actuation mechanism, brake oil circuit and electronic control module were designed based on the principle of little change and influence. In the end, the valve clearance adjustment was conducted and the parameters such as in-cylinder pressure, valve lift, pushing force, exhaust temperature and brake power were measured, which verified the brake performance and reliability of the designed scheme.