The utility model discloses a constant temperature and humidity deformeter. A detection device is right above a to-be-measured material. A transparent square closed cabinet and a water storage tank form an integrated cuboid side wall whose side wall is provided with a cavity. The upper end of the cuboid side wall which has a cavity is connected with an air heater, an air condenser, and a gas temperature sensor. Compared with the prior art, using the design scheme can achieve the following technical effects: the saturated solution of an inorganic salt used is easy to prepare, and the saturated solution can be repeatedly prepared and used, an electronic dial indicator used is fixed on the outer side of the top of a constant temperature and humidity cabinet, and the probe contacts with the to-be-measured material on the inner side, and the deformeter can realize real-time in situ monitoring of the to-be-measured material under set temperature and humidity. The device is a constant temperature and humidity deformeter which is high in precision and good in repeatability, and can perform real-time in situ monitoring.