For that i have change in Validation.js of magento
please find this code
['validate-password', 'Please enter 6 or more characters. Leading or trailing spaces will be ignored.', function(v) {
var pass=v.strip(); /*strip leading and trailing spaces*/
return !(pass.length>0 && pass.length < 6);
}],
and replace it with below code
['validate-password', 'Please enter 8 or more characters.Password should contain one numeric character, one capital letter
. Leading or trailing spaces will be ignored.', function(v) {
var pass=v.strip(); /*strip leading and trailing spaces*/
if (!(/[a-z]/i.test(v)) || !(/[0-9]/.test(v)) || !(/[A-Z]/.test(v))) {
return false;
}
return !(pass.length>0 && pass.length < 8);
}],