A method for reducing electromagnetic interference (EMI) in a system that periodically operates with a fixed sampling frequency includes reading a digital signal to which an analog signal received from a sensor is converted, generating a time delay that is modulated each cycle of the fixed sampling frequency with software, starting to execute a digital signal processing algorithm by applying the time delay that is modulated, and transmitting to another device through write of the digital signal. Accordingly, the EMI spectrum is spread through the time delay that is modulated with software, resulting in reduced EMI level.