Locomotive diesel engines have the typical characteristics of high-power intensified diesel engines, generally four-stroke V-type engines, with 12 and 16 cylinders being the most common, as well as in-line 6-cylinder, 8-cylinder and 10 cylinder. The width and height of diesel engine are limited by the gauge standard of railway rolling stock, and the allowable axle load of locomotive also limits the weight of diesel engine to some extent. Modern locomotive diesel engine constantly improves the degree of pressurization (see internal combustion engine pressurization), and at the same time increases the cylinder displacement. The single power of high-power diesel engine has reached 5000 kW, the average effective pressure is 1.3 ~ 2.0 MPa, and the fuel consumption rate is 200 ~ 225 g/(kWh). Accessories of diesel engine, such as cooling water radiator, fan and air filter, are arranged in the engine room, while oil filter and oil heat exchanger are generally arranged in the engine room. Almost all diesel engines use electric starting mode, and only a few use air starting. The speed control system mostly adopts hydraulic full-speed governor, and is equipped with automatic safety protection devices such as overspeed shutdown, oil pressure protection and overtemperature unloading.

The development direction of locomotive diesel engine is to continuously improve the power under the conditions of locomotive clearance and locomotive axle load. An important trend is to improve power by combining low compression ratio with two-stage supercharging. Improve reliability and durability, and prolong the life of diesel engine; Improve the economy, especially under partial load, transition condition and idle condition; Using electronic technology to realize working condition optimization and automatic fault monitoring; Reduce noise and harmful components in waste gas to prevent pollution; Follow-up to improve the supercharger of locomotive diesel engine.