A blood vessel scanning system and method are provided, which are adapted for user identification. The blood vessel scanning system is implemented for a head-mounted image viewing device. The blood vessel scanning method comprises the following steps: determining whether a user is authorized or not according to the blood vessel scanning image of the user； if the user is an authorized user, the blood vessel scanning system adjusts lens degree of the head-mounted image viewing device according to the pre-stored visual information of the user.
