In order to research on the influence of single submunition failure probability and the number of submunition on successive failure probability of underwater continuous explosion submunition group, theoretical analysis and simulation were conducted by probability theory and Monte-Carlo method. The results show that single submunition failure probability has great effect on successive failure probability of submunition group. With increase of submunition number, the successive failure probability of explosion submunition group will increase linearly. In view of groups with the submunition number 300 to 500, the appearance probability of 2 and more successive failure is 0.74% to 53.44%, the appearance probability of 3 and more successive failure is 0.00318% to 3.03% and the appearance probability of 4 and more successive failure tends to be 0 when single failure probability is 0.5% to 4%.