The jacking force of rectangular pipe jacking machine is an important parameter in jacking design, but there is no unified standard calculation formula at present. In this paper, the Bill Bowman theory and the theory of partial contact between pipe soil and slurry are modified and improved, and the shell frictional resistance of pipe jacking machine is calculated separately, based on which a new method for calculating the jacking force of rectangular pipe jacking machine with large crosssection is deduced. The comparative analysis is made between calculated value and the measured value of jacking force of the largesection rectangular pipe jacking machine used in Suzhou Chengbei Road, and the results show that: (1) The Bill Bowman′s theory suits for upper earth pressure calculation better. (2) When a stable mud set is formed, the head resistance of 1.1 times of the static earth pressure is highly consistent with the actual situation. (3) The jacking force per unit length calculated by the derivation method is close to the measured value, and the engineering applicability is good.