Abstract: Electromagnetic susceptibility (EMS) of cathode ray tube (CRT) for computer was investigated preliminarilyusing the test method of bulk current injection (BCI). During the test, CW signals as electromagnetic interference (EMI)signals with different amplitude at a certain frequency were injected into the RGB, horizontal synchronization (HS) andvertical synchronization (VS) signal line of video graphics array(VGA) interface. Sideling stripes came into view on the CRTdisplay when the HS signal line was injected into EMI signals. Moreover, the stronger the EMI signals, the more obvious thesideling stripes. The dependent relations between the injected signals and the coupling ones on the HS signal line were alsopresented.