The invention discloses a water jacket structure of a four-cylinder two-valve diesel. The water jacket structure comprises cylinder hole water jackets and cylinder cover water jackets. The cylinder hole water jackets comprises the first cylinder water jacket, the second cylinder water jacket, the third cylinder water jacket and the fourth cylinder water jacket. A diesel thermostat is arranged in the position close to the first cylinder water jacket and the second cylinder water jacket. The height of a water jacket cavity of each cylinder hole water jacket is 70%-80% of the piston stroke. Every two adjacent cylinder hole water jackets are connected through a machined through hole. Water inlet holes corresponding to cylinder holes are formed in the bottom ends of the front sides of the cylinder hole water jackets. Water filling holes between the cylinder hole water jackets and the cylinder cover water jackets are formed in the top ends of the rear sides of the third cylinder water jacket and the fourth cylinder water jacket. The lower half portions of outer side cavities of the first cylinder water jacket and the fourth cylinder water jacket are disconnected. The water jacket structure is low in resistance, high in flow velocity, uniform in cooling and good in nose bridge area radiating.