The results of studies of the temperature dependences of the magnetic properties and magnetic field behavior of thin-film three-layer Co/Gd/Co system, obtained by ion-plasma magnetron sputtering, are present. The thickness of the cobalt layers is 5.0 nm, and the thickness of the Gd layers, tGd, varies from 3.0 to 10.0 nm. The bulk magnetic characteristics of the samples are measured on a vibrating magnetometer at the external magnetic field oriented parallel to the plane of the samples. The influence of the temperature and Gd thickness on the shape of the hysteresis loops, the values of the magnetic moment m and coercive force are discovered. In particular, with the temperature changes from 100 to 300 K, the decrease of the coercive force is observed. At a temperature above 150 K, magnetic moment increases. With increasing thickness of gadolinium, the value of m decreases.