Abstract: For the sake of fulfilling the increasing demands on high-pressure vessels, and discussing further on the techniques in their manufacture, we started the research works since the end of 1956. The first mission of our works was to use cast-steel instead of forged steel as the construction material for high-pressure vessels. To do this, we had to prove such possibility both theoretically and experimentally. The second mission was to apply the theory of plasticity of metals to autofrettage the vessels. Obviously, this process of autofrettage is a well-known means to increase the yield strength of any construction material of plastic metals. However, the application of this principle to a high-pressure vessel is a new subject. Although we knew that the technique of autofrettage has only been discussed theoretically, we did begin our experiments both in laboratorial and commercial scale in 1957. The experimental results were consistent with our mathematical deduction. The stresses along the wall thickness of the vessels were more uniformly distributed after the autofrettage treatment, and the material itself was strengthened. Obviously, there are certain deffects in the cast-steel; the small pieces into which it will break under high-pressures may have considerable killing and destroying damage. Hence in the international literatures, high-pressure vessels made of cast-steel are available only for low pressure purposes, and in some cases are even forbidden to use for pressure vessels. But disregarding the conventional rules given by the literatures, our research workers have succeeded in the manufacture of cast-steel pressure vessels. At present, the approved cast-steel high-pressure vessels are welcome everywhere in China, and in many places, these cheap, good, safe and quick-produced vessels are already put into mass production for industrial purposes.