Abstract: During the transit of comets （Halley, Hyakutake and Hale-Bopp）, some data analysis and statistical research have been made and the possible influence of magnetospheric environment resulted from the 5 times transit of the 3 comets have been discussed. According to the feature of cometary plasmas, the possibility is pointed out in this paper that cometary tail is able to cause the magnetospheric disturbance. However, the disturbance is restricted by some rigorous condition, and it is not essay for the comets to possess such condition during their transit.