The invention discloses an air conditioner and an air indoor unit control device thereof and a control method. The control device comprises an acquiring module for acquiring running parameters of an indoor unit and/ or current indoor environment parameters when the air conditioner runs in a refrigerating mode, an air bypassing module for bypassing the air of an indoor blower, and a control module which is correspondingly connected to the acquiring module and the air bypassing module and used for controlling the air bypassing module according to the indoor unit running parameter and/ or the current indoor environment parameter so as to adjust the air, flowing through an indoor heat exchanger, of the indoor blower. With the adoption of the control device, the system can be kept in an outstanding function demand state; the unsteady running state caused by unnecessary temperature decrease can be reduced, thus the system is outstanding in dehumidifying effect and environmental temperature stability, and as a result, the comfort of the system is improved.