Abstract: In view of the problems of using only hr to determine the protection range of h in the rolling ball method,such as the protection range of single branch h is wide in transverse and narrow in longitudinal, protection range is uncertain, only applicable to h≤hr, and using hr of different sizes to determine the protection range between two branches h, according to the lightning strike ability of the rolling ball and the protection ability of h, the problems existing in the protection range of single branch h and two branches h of the rolling ball method are analyzed, and the improvement of using the hr and the protection ability of h to jointly determine the protection range is put forward for discussion. The analysis shows that the transverse part of the protection range of single branch h by rolling ball method exceeds the protection ability of h, and there are lightning protection loopholes. The longitudinal narrow part reduces the protection range; The protection range between the two branches h determined by large hr is too wide, and the use of small hr will lower the height of the protected object, which is unreasonable. The improved rolling ball method can be applied to any height of h, and the protection range between single branch h and two branches h is within the protection ability of h, and the protection range is reasonable.