Abstract: To meet the requirements of rapid rescue when mine water flooding occurs, a new type of mine high speed rescue pump with small volume, large flow and high head was proposed in this paper.The whole structure was a combination of upper motor and lower pump.With the same flow rate and head, the length and weight of the prototype were reduced by 31% and 51.2% compared with the pump in the current market.Taking the 1 250 kW series as an example, according to the current structure of the variable frequency high speed motor, two cooling circuits were proposed which included the positive and reverse circuits.Based on the k-ω turbulence model and the total heat transfer model, the internal flow field and temperature field of the two circulating loops were numerically simulated by solving the three-dimensional N-S equation and energy equation.The numerical simulation results showed that:it was found that the pressure drop were 109.95 m in the positive circuit and 107.83 m in the reverse circuit.In the respect of pressure distribution, the lowest pressure region appeared at the bottom of the thrust plate in the both circuits.However, in terms of the lowest pressure in the circuit, the value for positive circuit was -1 584.2 kPa which was much smaller than that in the reverse circuit with the value of -107.03 kPa.In the respect of tem-perature field, the highest temperature always appeared at the film of the bearing.In the positive circuit, the temperature was 56.26 ℃, which was 0.91 ℃ less than 57.17 ℃ in the reverse circuit.Considering avoiding cavitation, the reverse circuit was adopted for cooling.Finally, the hydraulic performance and temperature rise characteristics in the motor chamber of the pump designed by reverse circulation loop were verified by experiments.The experimental results showed that the hydraulic performance of the pump accorded with the design conditions.In the performance, the highest temperature in the motor chamber was 51.25 ℃; in the life test, the temperature varied from 50.34 ℃ to 51.15 ℃.The temperature range could meet the cooling requirements for the variable frequency high speed motor of 1 250 kW.