The production and construction of mainstream diesel engine workshops in China are introduced. Based on the example of medium-speed diesel engine, the current domestic situation and shortcomings of the parts machining, assembly and overall test of medium-speed diesel engine are summarized and analyzed. The manufacturing process of marine diesel engines can be improved by improving the workshop environment, optimizing equipment configuration, rationally adjusting process flow, adopting modularization and integration concept, so as to ensure the quality, reliability and production efficiency of the diesel engine.