The most important technology in Numerical Control (NC) system is trajectory interpolation algorithm, and the machining accuracy of NC machine tool is directly affected by interpolation algorithm. Digital integral algorithm and parameter interpolation algorithm are two commonly used interpolation algorithms. In order to compare the accuracy of two interpolation algorithms, two kinds of interpolation algorithm models were established, and to use the common lines and arcs as interpolation objects, through calculation and comparison, it was concluded that the error of parametric interpolation algorithm was smaller and had higher precision when high frequency and high precision were obtained, and the error formula was given. The result has certain reference significance for engineering practical problems, which also provides the necessary theoretical basis for the pursuit of higher precision interpolation in the future.