The shock tester based on a three-body, single-level velocity amplifier is especially suitable for high-g shock tests of lightweight and compact pieces. This study focuses on disclosing some key technologies that affect whether the velocity amplifier could achieve a high-g level shock experimental environment. Equations describing the first collision are deduced and some key design criteria are proposed. The key conditions for formation of the opposite collision are proposed for the second collision, which is the most important point, to obtain a high-g shock environment. A test platform was constructed, and experiments were conducted with different shock rods, pulse shapers, and initial velocities. The test results fully demonstrated the powerful ability of the single-level velocity amplifier for high-g shock experiments and tell us that a duralumin alloy or carbon fiber is suitable to design shock rods.