The error model best estimation of trajectory(EMBET)based on the constraint of basis function is an important method for post-mission high-precision data processing of external ballistics.It is significant to choose an appropriate basis function for obtaining ballistic parameters and analyzing ballistic characteristics effectively and accurately.To explore the effect of basis function on the accuracy and efficiency of data fusion for external trajectory data,the EMBET data fusion methods characterized by cubic B-Spline basis function and two-point cubic Hermite basis function were compared and analyzed.Firstly,the trajectory was characterized by two basis functions.Therefore,the data fusion for trajectory measurement data was transformed into the estimation of basis function coefficients.Thus,the fusion model of external trajectory was solved.Combining the theoretical ballistic characteristics of weapon systems,the data fusion methods based on the two basis-functions were simulated and compared through fusion instance.The accuracy was also compared and analyzed according to the ballistic coordinate,ballistic velocity and error detection of measurement elements.The simulation results show that,under the same conditions,both of the data fusion methods based on the two basis functions can achieve high-precision external ballistics coordinate parameters.But the data fusion method based on the basis function of B-Spline is more advantageous in compression of estimated parameters and calculation efficiency.Furthermore,the calculation accuracy of its ballistics velocity parameters is higher than that of the other method.