A fractional order Smith predictive control approach based on the inverted decoupling is proposed for non-square systems with time-delay. Firstly, inverted decoupling is extended into $m\times n$ non-square systems. The design method of the inverted decoupling matrix is proposed. At the same time, to ensure the decoupling matrix stable and regular, the realizability conditions and the compensation method of the controlled object are provided. Then, we design a fractional order Smith predictive controller for decoupled signal-loop systems. The design method of the fractional order controller is simplitied using the equivalence relation between the IMC(internal model control) and the Smith predictive control. Furthermore, we propose a tuning methodology for controller parameters based on the maximum sensitivity. Finally, the typical Shell standard control problem is studied to verify the effectiveness of the proposed method. The simulation results show that the proposed method is not only simple in design and easy to implement, but also convenient in parameter tuning, and has a better tracking performance, disturbance rejection property and robustness.