The corridor resource is very tight, the situation that HVDC lines and AC lines HVDC lines are parallelly erected with AC lines. Set up the electromagnetic coupling model of AC/DC lines which is parallel or same tower by the electromagnetic transient program. Calculate the fundamental frequency induction current of dc line and ac/dc side voltage and current distortion rate, analyzed the influence of parallel AC and DC line to core saturation instability, and studied the measure for limit the induced current on dc line.