The invention relates to a main road and side road matching method of a navigator. The main rod and side road matching method comprises the following steps of: if a present vehicle runs on a main road and an exit leading to a side road on the right side of the main road exists within 2Km of the front part of a present vehicle, acquiring a running lane image of the main road in real time by a CPU (central process unit) of the navigator through a camera arranged at the back of the present vehicle so as to judge that whether the present vehicle is located in a running lane at the rightmost side of the main road or not; if the present vehicle is located in the running lane at the rightmost side of the main road, judging whether a running lane line of the running lane image generates clockwise deflection in real time or not when the present vehicle is about to reach the exit; if the running lane line generates the clockwise deflection, judging that the present vehicle enters the side road by the CPU; matching a present running path to the side path through the navigator; and if the running lane line does not generate the clockwise deflection, judging that the present vehicle still runs on the main road.