In mode division multiplexing systems based on few-mode fibers, it is inevitable to carry out the fusion splice between the few-mode fibers. Precise measurement of mode coupling at each splice point can provide reliable bases for evaluating welding-quality and positioning faults of the system. We analyze the mode coupling characteristics at a splice point between few mode fibers based on Rayleigh backscattering theory, then build a measurement system of mode coupling at a splice point based on the structure of a photonic lantern and an optical circulator, and successfully measure the mode coupling at a splice ponit between two pieces of three modes fibers(the lengths are 0.9 km and 9.8 km, respectively). The experimental results show that the mode couplings at the splice point are respectively -14.9 dB and -13.9 dB with the offset distances of 1.5 μm and 2 μm.