The multi-body dynamics of cislunar space is an important research direction of spacecraft motion in nowadays. DRO (Distant Retrograde Orbit) is a high value orbit in cislunar space. The initial value of the plane DRO at CR3BP (Circular Restricted Three-Body Problem) includes the x-component position, y-component velocity, and period. Under the traditional differential correction method, if the x-component position is fixed, the y-component velocity and period need to be input as the variables to be corrected. In this case, the approximate value of the y-component velocity and the period need to be calculated in advance. An improved method for cislunar space DRO calculation based on differential correction is proposed. This method calculates the period by setting the orbital integral event, and updates the period in each correction, so as to obtain the exact value of the period in the process of correcting the y-component velocity. This method reduces the input of the period to be corrected so that reduces reliance on the period. Under the condition of fixed x-component position, the initial value and period of the orbit can be calculated by inputting only one parameter (y-component velocity) while traditional differential correction needs two (y-component velocity and period). In this study, the stability, Jacobi energy, precision and other indexes are analyzed between traditional differential correction and improved differential correction.