A signal processing method is provided and includes the following steps. A first synchronizing signal having a synchronizing frequency and a next expected pulse with an expected rising edge is provided. A second synchronizing signal having a selected frequency being within a frequency range is produced when the synchronizing frequency of the first synchronizing signal is out of a frequency range. A third synchronizing signal having a first pulse with a first rising edge is produced when the synchronizing frequency is within the frequency range, wherein the first rising edge is produced at an expected time point. Whether the next expected pulse appears in a period from the expected time point to a certain time point is detected as a detecting result. And a first falling edge of the first pulse is produced based on the detecting result. A picture-field flicker phenomenon of an LCD is eliminated through the method.