The invention provides a diesel engine thermostat structure and assembly way. Particularly, a cross beam and two stand columns with grooves are added in a thermostat cover, an upper valve is arrangedat the upper part of a thermostat body, bosses are symmetrically arranged at the two ends of the lower part of the thermostat body, and a water outlet connecting pipe is connected to a water outlet atthe lower end of a thermostat base. A thermostat push rod is embedded in a push rod groove in the center of the thermostat body, and the upper end of the push rod is propped below the cross beam of the thermostat cover. The two bosses at the lower part of the thermostat body are clamped in the grooves of the two stand columns of the thermostat cover, and the thermostat body is fastened. When thetemperature of the engine coolant reaches a specified value, the thermostat push rod pushes the upper valve downwards to be opened, and at the moment, the flow area of the water outlet is much largerthan that of a common thermostat. According to the modular design of the thermostat structure, the matching requirement of a high-configuration engine with small front end space can be met. The structure is quite compact, the design is reasonable, the appearance is attractive, assembly and maintenance are convenient, and the problem that component arrangement is difficult due to the small engine space is effectively solved.