The multistage noise-shaping (MASH) delta-sigma modulator (DSM) is the key element in a fractional-N frequency synthesizer. A hardware simplification method with subtraction inversion is proposed for delta-path's design in a MASH delta-sigma modulator. The subtraction inversion method focuses on simplification of adder-subtractor unit in the delta path with inversion of subtraction signal. It achieves with less hardware cost as compared with the conventional approaches. As a result, the hardware organization is regular and easy for expanding into higher order MASH DSM design. Analytical details of the implementation way and hardware cost function with N-th order configuration are presented. Finally, simulations with hardware description language as well as synthesis data verified the proposed design method.