Coxsackies Al6 virus is one of main cause of hand food and mount disease (HFMD) in Vietnam. In order to having the virus seed system produced vaccine, the authors carried out the study of adaptation of CVAl6 strains in Vero cell. The results show that 2/10 virus strains developed the best in vero cell from the first passage, they are CA-04 and CA-08 strains. They were selected for cloning. The cloning result was selected 2 clones growing well in verro cell that is CA-08-4-3-1 and CA-08-4-3-2. Those 2 clones were passaged 30 consecutive times in vero cell, they growned well with high virus titer.