i have gained one year exp by working as an accountant in canada and now i am eligible to apply for cec application.
is it possible can i change my current job now?
Depends on the type of work permit you have. If it is a TWP, then you would have to obtain a new work permit before you could start a different job. Guessing you're on a PGWP, tho, since you only have 1 year of experience.
will this have any affect on my application?
It should not have any effect on your application, assuming you have correctly assessed your eligibility. You can change jobs anyway, not a problem, as long as the experience is skill level 0,A or B.