Medium consistency pump (MC pump) is the core equipment of medium consistency pulp transportation,and the efficiency of delivery system is directly determined by pump performance. In order to investigate the operation and performance characteristics of MC pump in different conditions,a MC pump test bed is established using sonar flowmeter and monitoring system. The head,efficiency,gas fraction and max flow rate are studied with pulp concentration 7.52%,9.3%,12.1%,speed 960 r/min,1 140 r/min,1 500 r/min and different degas vacuum degree at vacuum housing. The results show that at constant flow rate,pump head and efficiency decrease with increase of pulp concentration. Vacuum degree has significant effect on pump performance. MC pump can pump concentration 7.52% pulp without vacuum,but pump head and efficiency decrease obviously with flow rate increasing. With vacuum degree increasing pump head increases,and gas fraction decrease at pump outlet. Head increases with rotation speed increasing,but gas fraction of pulp decreases at pump outlet. Vacuum degree decreases with rotation speed increasing,so enhancing pump speed can improve gas-liquid separation. Gas fraction and degas vacuum degree increase with concentration increasing. The max flow rate decreases with increase of concentration and increases with rotation speed increasing.