The utility model relates to an adjustable zero-pressure multifunctional baby fixing cap which structurally comprises a rear half portion and a front half portion which are designed to be of an integrated structure. The side edge of the rear half part is provided with a Velcro adhesive tape hook surface; the side edge of the front half part is provided with a Velcro adhesive tape rough surface matched with the Velcro adhesive tape hook surface; the rear half part is composed of a rear-end moisture absorption and heat preservation part and a rear-end ventilation and heat dissipation part; the front half part is composed of a front-end moisture absorption and heat preservation part and a front-end ventilation and heat dissipation part. The size of the cap can be conveniently adjusted according to the size of the head of a baby; after the cap and the oxygen pipe are fixed, the head of the baby can still be conveniently observed in real time; compression of a common hat on the head of a baby is reduced, the heat preservation performance and breathability of the hat are improved, and the wearing comfort of the baby is improved.