For a class of single input single output dual-rate sampling system with output delay, this paper presents a robust iterative learning control algorithm. The dual-rate sampling system with output delay is transformed into state-space model in slow sampling rate without time-delay in form by using the lifting technology, and based on the two dimensional (2D) system theory, the iterative learning control process is turned into an equivalent two dimensional models. Then, the sufficient conditions for the stability of system and the design method of robust controller are given in terms of linear matrix inequalities(LMI) technique. Finally, the liquid level control simulations of three tank systems demonstrate the feasibility and effectiveness of the proposed method.