The hydraulic systems own the large torque to volume ratio. Therefore, they are widely used in steel manufactory. The analog Integral variable structure control has been successfully simulated on the electrohydraulic servo control. Due to the wide application of hydraulic components in industry needing higher torque, this paper extends the research to the digital implementation. For the digital implementation, the discrete existence conditions of sliding mode are introduced to adapt the IVSC to the discrete systems. The system equations are also extended to more general forms. Due to the great development in ASIC, the proposed control rule is implemented by the CPLD chips. Experimental results will show the discrete integral variable structure control has the robustness to against the parameter derivations and disturbances. The prototype board also shows the practical capability of the proposed method. 2004 Elsevier Ltd. All rights reserved.