In order to realize the analysis of the initial value of the variable focal power lens(VFPLs) for the zoom system, the aberration of the VFPLs for the zoom system is analyzed. The primary aberration of the zoom system is determined according to the aperture angle of the beam and the height of the object. The relation between the shape parameters and the magnification of the zoom system is analyzed by using the theory of thin transparent image difference, and the initial value of the zoom system is determined by using the minimum value of spherical aberration and coma. The results show that the calculation equation of the magnification and shape parameters of the zoom system can reach the requirements of determining the initial value of the VFPLs in the zoom system, and it is simple, fast and reliable, which provides a reference for further computer correction of the aberration of the zoom system.