Abstract: Touches off the parallel connected pulse forming lines one by one, use silicon diodes to isolates the high voltage pulses, several single square pulses can be combined to form a MHz repetition rate multi-pulses string. The structure of the confluence box, which the silicon diodes are putted into, affects the life-time of diodes and the pulses' risetime of accelerate voltage clearly. This paper describes the simulations and high-voltage experiments to study the correlation between the confluent structure and the pulses confluent effect, and introduces the final confluent system of the three-pulses LIA "Dragon II".