Electrical steel cores in electric motors are often operated under variable temperature conditions, and the temperature has a large impact on the magnetic properties of electrical steel. Different Silicon content also makes electrical steel have different performance characteristics. Therefore, in this paper, an environmentally adjustable electrical steel magnetic property testing system is built to investigate the magnetic property variation of non-oriented electrical steel sheets with different Si contents at different temperatures. Through the experiments in this paper, it is found that the trend of magnetic properties of electrical steels tends to flatten out with increasing Si content under the influence of temperature. In particular, the loss of 6.5% Si shows a trend of first decreasing and then increasing with the increase of temperature. The internal grain structure of electrical steel can explain this phenomenon very well. The larger the grain size, the less the magnetic properties of electrical steel are affected by temperature. In order to further analyze the variation phenomenon of electrical steel loss, the loss separation calculation was carried out for 5 more electrical steels with different Si content in this paper. The reason for this phenomenon was finally explained by a special preparation process of 6.5% Si.