Does graystripe die in the warrior series?

no.

SPOILER ALERT

but he gets stolen by two-legs. with the help of a kitty-pet named milly he finds his way to the lake where his clan welcomes him. he returns to find out that Brambleclaw has been made deputy in his absence. after thinking for a while Firestar decides that brambleclaw would remain deputy as he knows the clan better.

SUPER SPOILER ALERT

After Firestar dies Brambleclaw becomes Bramblestar and Squirrelflight becomes deputy. Greystripe stays a normal warrior.