On the basis of analyzing the pattern data produced by the AutoCAD, CorelDRAW, and AI drawing software, the line turning point algorithm for pattern data, and reversing sewing and contracting sewing for non closed graph, and reinforcing sewing for the closed graph and the other customized algorithm were designed and implemented. The control algorithm of unilateral inflection point deceleration for the pattern data was studied and put forward. Test results show that the algorithm can efficiently and stably complete transformation from key point data of pattern pattern to pattern sewing point data. At present, this algorithm has been applied in pattern sewing machine software "intelligent software".