A respiratory system, including: a gas supply unit including a gas supply port; and a heating and humidifying unit being detachably combined with the gas supply unit, the heating and humidifying unit being electrically connected to the gas supply unit when combined with the gas supply unit, wherein the heating and humidifying unit includes: a base including a control element; an adapter combined with the base and able to rotate at least 90 degrees relative to the base, wherein the adapter is electrically connected to the control element; and a water tank being detachably combined with the base, the water tank including a gas inlet and a gas outlet, wherein when the water tank is combined with the base, the gas inlet penetrates through an aperture of the base to be fluidly connected to the gas supply port, and the gas outlet is fluidly connected to the adapter; characterized in that the base further includes a fixing portion for combining with the adapter, the fixing portion includes a through hole and an inner wall, and the inner wall protrudes from a surface of the base and surrounds the through hole; and wherein the fixing portion further includes a groove and at least one drain hole, the groove surrounds the through hole and the inner wall is located between the groove and the through hole, and the at least one drain hole is located at a bottom of the groove. a gas supply unit including a gas supply port; and a heating and humidifying unit being detachably combined with the gas supply unit, the heating and humidifying unit being electrically connected to the gas supply unit when combined with the gas supply unit, wherein the heating and humidifying unit includes: a base including a control element; an adapter combined with the base and able to rotate at least 90 degrees relative to the base, wherein the adapter is electrically connected to the control element; and a water tank being detachably combined with the base, the water tank including a gas inlet and a gas outlet, wherein when the water tank is combined with the base, the gas inlet penetrates through an aperture of the base to be fluidly connected to the gas supply port, and the gas outlet is fluidly connected to the adapter; characterized in that the base further includes a fixing portion for combining with the adapter, the fixing portion includes a through hole and an inner wall, and the inner wall protrudes from a surface of the base and surrounds the through hole; and wherein the fixing portion further includes a groove and at least one drain hole, the groove surrounds the through hole and the inner wall is located between the groove and the through hole, and the at least one drain hole is located at a bottom of the groove. a base including a control element; an adapter combined with the base and able to rotate at least 90 degrees relative to the base, wherein the adapter is electrically connected to the control element; and a water tank being detachably combined with the base, the water tank including a gas inlet and a gas outlet, wherein when the water tank is combined with the base, the gas inlet penetrates through an aperture of the base to be fluidly connected to the gas supply port, and the gas outlet is fluidly connected to the adapter; characterized in that the base further includes a fixing portion for combining with the adapter, the fixing portion includes a through hole and an inner wall, and the inner wall protrudes from a surface of the base and surrounds the through hole; and wherein the fixing portion further includes a groove and at least one drain hole, the groove surrounds the through hole and the inner wall is located between the groove and the through hole, and the at least one drain hole is located at a bottom of the groove.