The invention discloses a space
environmental temperature and
humidity control method and a control device thereby. In the method, a controller controls the operation of an actuating mechanism used for adjusting temperature and
humidity according to temperature and
humidity monitoring results so as to control the temperature and humidity of air; according to the required temperature and
relative humidity of a target space, a set air
dew-point temperature value of a mixed air section is set in advance in a storage; the controller compares a monitored air
dew-point temperature monitored value of the mixed air section, which is monitored by a
dew-point temperature sensor, with the set air dew-point temperature value of the mixed air section, which is set in advance, and judges whether the actuating mechanism is used to cool the air to lower the humidity or not; and after the adjustment decision is made, a
temperature control procedure starts. Since the monitoring adjustment
decision making step of the air dew-point temperature value of the mixed air section is repeated according to a set cycle in the running process of an
air conditioning unit, the method can carry out necessary control of lowering humidity, raising or reducing temperature as required. The invention not only can greatly save energy, but also can stabilize a
control system and realize high-accuracy control by using the
control system, the
temperature control and the humidity control of which are not interfered.