The utility model discloses a multistage middle-open type centrifugal pump axial force balance structure. A plurality of impellers of odd number are assembled on a pump shaft, the impellers of odd number are divided into two groups, two groups of the impellers are opposite in direction, and one group of the impellers are more than the other group of the impellers by one. An interstage ring and an interstage sleeve are assembled between two groups of the impellers, wherein the interstage sleeve is arranged on the inner side of the interstage ring, and outlets of two groups of the impellers are communicated through gaps between the interstage ring and the interstage sleeve. A pressure relief ring and a pressure relief sleeve are assembled between a second suction chamber and a second throat bushing, wherein the pressure relief sleeve is arranged on the inner side of the pressure relief ring, a balance pipe is connected from an empty cavity formed by the second throat bushing and the pressure relief ring and the pressure relief sleeve and is communicated with a first suction chamber, and therefore the second suction chamber is communicated with the first suction chamber through gaps between the pressure relief ring and the pressure relief sleeve and the balance pipe. Outer diameter change of the interstage ring and the pressure relief ring is utilized to form balance of rotor axial force. The multistage middle-open type centrifugal pump axial force balance structure has the advantages of being simple, easy to achieve and good in axial force balance effect.