This standard specifies the basic parameters, types, dimensions, technical requirements, load-bearing capacity and selection methods of cylindrical gear reducers. The reducer specified in this standard is suitable for the transmission of various types of mechanical equipment in metallurgy, mining, transportation, cement, construction, chemical industry, textile, light industry, energy and other industries. The speed of the high-speed shaft of the reducer is not greater than 1500 r/min. The peripheral speed of the reducer gear transmission is not greater than 20 m/s. The working environment temperature of the reducer is -40~+45℃. When the working environment temperature is below 0℃, the lubricating oil must be heated to above 0℃ before starting. When the working environment temperature is higher than 45°C, heat insulation and cooling measures must be taken.