This paper present a new design of a Limited angle torque motor (LATM) with Dual Halbach Arrays for rotary direct drive valve (DDV), which needs high frequency response, high power to weight ratio. Reluctance model of proposed LATM is discussed. The structure parameters are optimized by particle swarm optimization (PSO) method to improve performances, especially the output torque. The optimized parameters are validated by the FEM method. It is shown that the new design improves the output torque significantly.