Multivariable non-square system with time delays often arises in the chemical production process. Owing to the matrix that is adopted to describe non-square system is not square, many classical multivariable control methods can be hardly applied in such system. In this paper, based on Non-square effective relative gain (NERGA) a novel decentralized PID control method is proposed. The input and output loops of the non-square system are paired though NERGA firstly, and then strong robust decentralized multivariable proportional-integral-differential (PID) controllers are designed individually based on the squared models. Finally, Simulation study was carried out for three inputs and two outputs system, the simulation results can demonstrate the effectiveness of the proposed method.