A lamp assembly and an air guide plate thereof. The lamp assembly and the air guide plate are positioned in a projector. The lamp assembly comprises a base with a bottom portion and an opening, and a lamp with a bulb disposed at the bottom portion in a manner such that it extends toward the opening. The air guide plate comprises a body, a first guide portion, a second guide portion, and a third guide portion. The first guide portion substantially extends between the bulb and the bottom portion. The second guide portion substantially extends toward the bulb. The third guide portion substantially extends between the bulb and the opening.