This paper presents a generating algorithm at pixel level for parametric curve. The parallel particle sub-swarm optimization is used to search the optimal step of curve in forward. Large amount of repeated computing for points are avoided and the result is precise enough. Simulation results show that the parallel method based on particle sub-swarm can be used for searching the optimal step of parametric curve with any degree quickly. At the same time, compared with other methods, this algorithm produces the maximum step efficiently. Since there is no restriction on control point position and curve degree, the algorithm can be extended easily to other parametric curves besides Bézier curves.