The invention relates to an air conditioner indoor unit capable of improving indoor humidity environment. The air conditioner indoor unit comprises an intake port, an exhaust port and an indoor heat exchanger; the indoor heat exchanger comprises a main heat exchanger and an auxiliary heat exchanger serially connected with each other; the auxiliary heat exchanger is near the exhaust port; a main electronic expansion valve is arranged on a pipeline between the main heat exchanger and the auxiliary heat exchanger; an auxiliary electronic expansion valve is arranged on a pipeline between the auxiliary heat exchanger and an outdoor unit; and the intake port is provided with an indoor fan. The air conditioner indoor unit is reasonable in design, simple in structure and convenient to control, canincrease the dehumidifying quantity and adjust the exhaust temperature during dehumidifying, can increase indoor humidity during heating to greatly improve the product use comfort, and deserves popularization.