A medical air mattress has a mattress body (30), a lower bedspread (10), an upper bedspread (50) and a guardrail unit (60). The mattress body (30) is formed by multiple air cells parallelly arranged in an air cell row. The upper bedspread (50) covers the mattress body (30) and has two guardrail sleeves (52) formed on the upper bedspread (50). The guardrail unit (60) has multiple guardrail air cells (61) mounted respectively in the guardrail sleeves (52). Since the guardrail sleeves (52) are formed on the upper bedspread (50), the guardrail sleeves (52) from each opposite side of the upper bedspread (50) will draw each other to maintain the guardrail sleeves (52) in position when pressed. Therefore, the guardrail sleeves (52) do not fall down when pressed to remain providing optimal protection purpose.
