What happens to the equipment worn and carried by a
character polymorphed* into another creature capable of
wearing and carrying the same gear? What if the new
creature’s size is different?
Unless stated otherwise, all spells in the polymorph chain
function as described in the alter self spell description, which
states that if the new form is capable of wearing or holding the
item, it remains worn or held; otherwise it melds into the new
form and becomes nonfunctional. A human polymorphed into
another Medium humanoid-shaped form (such as an elf,
grimlock, or bearded devil) can wear or hold all his gear, so it
remains in place.
However, this is one of those times when size definitely
matters, since your gear doesn’t automatically change size as a
result of polymorph. Assuming the new form has appropriate
body locations—for instance, a human polymorphed into a troll
or a pixie—most of your magic items (rings, cloaks, boots, and
other items of magic clothing or jewelry) still fit just fine
regardless of your new size (see “Size and Magic Items” on
page 213 of the DUNGEON MASTER’s Guide).
嗯，官方FAQ上说明了的
