The phase function of a target curve is obtained using the Legendre transform and used to determine the position of graded grooves. In addition, the spatial arbitrary bending beams are generated by the interference of surface plasmon polaritons propagating on graded grooves. The effects of structural parameters are investigated. The results show that the intensity, shape and distance of propagation of spatial arbitrary bending beams rely on the constancy of target curve and the depth and width of the grooves.