We have more important significance studying quadratic rational b - spline curve ' s curvature monotony . this paper derive the curvature monotony condition for the quadratic rational b spline curves by using the skew coordinate system that can reduces the calculation process . and the curvature monotony condition is compared to the quadratic rational bezier curves " 本论文通过建立斜坐标系，简化了计算过程，推导出了二次有理b样条曲线曲率单调充要条件，并与二次有理b zier曲线的曲率单调条件相比较，结果表明：二次有理b样条曲线曲率单调的充要条件与二次有理b zier样条曲线相类似，但其条件又有不同。
