In this article, a systematic approach is proposed to design PI/PID-based multivariable control systems in which the designs and analyses of decentralized, decoupling, and sparse control schemes are all treated under a unified framework. First, based oil the relative normalized gain array (RNGA), a best loop pairing is obtained using the RGA (relative gain array)-Nederlinski index (NI)-RNGA rules. The index matrix is then calculated, and the control Structure is determined according to a selection criterion. Finally, the selected loop controllers are independently designed based oil equivalent transfer functions. The effectiveness of the proposed design approach is verified by analysis of several multivariable industrial processes, demonstrating that the selected control Structure results in better overall system performance.