查到了， 申請medicare是可以提前三個月申請， 到65歲生日的那個月才可以用上

Generally, you're first eligible to sign up for Part A and Part B starting 3 months before you turn 65 and ending 3 months after the month you turn 65. If you sign up for Medicare, stop your Marketplace coverage so it ends when your Medicare coverage starts. See how to change from Marketplace to Medicare.