Coherent control of fragmentation of CH3I using shaped femtosecond pulse train is investigated.The dissociation processes can be modulated by changing the separation of the shaped pulse train,and the yield of I+ under the irradiation of the optimal pulse is significantly increased compared with that using the transform-limited pulse.We discuss the control mechanism of dissociation processes with coherent interference in time domain.A three-pulse control model is proposed to explain the counterintuitive experimental results.