In this paper, a novel Magnetorheological (MR) valve with a tunable resistance gap that varies from minimum 1 mm to maximum 2 mm was designed. In addition, a mathematical model of the pressure drop between the inlet port and the outlet port for the proposed MR valve was developed. Magnetic simulation was conducted and combined with the pressure drop calculation using the derived MR valve model. The influences of the MR valve geometric parameters, such as the valve body thickness, the winding groove depth and the large end of radius of the valve sleeve on the valve performance were analyzed. The relevant results will provide the theoretical basis for the MR valve size design and structure optimization.