According to the working conditions of mine transport machinery,a reducer of bevel- cylindrical gear named JS75- 25 is developed. The key points for optimal design and the matters needing attention are given. According to the inspection specification of mining reducer,the type test of the prototype is carried out,the corresponding experimental data is gained. The data analysis of the heat balance under non- load,full load and the transmission efficiency of the gear reducer are carried out. The analytical results indicate that they have a high fitting precision in the heat balance and transmission efficiency perfectly matching exponential distribution curve,and so it can be used in a forecast of the correlative experimental data. According to the presented key points of design and experimental method,a basis for improving this kind of reducer is provided.