Abstract: Due to the electromagnetic compatibility problems of a typical digital signal controller (DSC), a method that analyzes the electromagnetic characteristics and temperature characteristics simultaneously is presented. The ambient temperature effect on electromagnetic susceptibility is studied. Based on the structure of behavior electromagnetic susceptibility model, the mechanism of electromagnetic interference is analyzed, and the influence which ambient temperature exerts on the mobility and threshold voltage of metal-oxide-semiconductor (MOS) transistors in DSC is derived. Combining the method of direct power injection and temperature control, the varieties of characteristic parameters of each part in susceptibility model at different temperatures is measured and simulated, revealing the internal factors of the susceptibility changes. Then, the threshold of DSC electromagnetic susceptibility is measured. Results show that the mobility and threshold voltage of MOS transistors in DSC immunity behavior is changed with ambient temperatures, which leads to the drift of DSC electromagnetic susceptibility.