The present invention belongs to the technical field of geometric modeling, and discloses a method and a system for constructing an interpolation curve or a curved surface based on a B-spline. The system comprises: a function deployment module, a telescopic translation module, a curve generation module, a central processing module, a curve smoothing module, a curve fitting module, a data storage module, and a display module. According to the technical scheme of the present invention, by using the curve smoothing module, a smoothing operation is performed on the curve in the image, the unsmoothcurve segment in the image can be effectively smoothed, and the curve after being subjected to the smoothing operation has substantially no defect with respect to the original curve, does not deviatemuch from the actual curve, and can adjust the degree of smoothness of the curve by adjusting the interval size by itself; and at the same time, by using the curve fitting module, the mapping reconstruction of the rotary part along the direction of the rotation axis can be realized, the data processing process can be simplified in a facilitated manner, and the consumption of computer resources can be reduced.