The invention discloses a method for synchronously obtaining a surface electromyogram by eight channels. The method comprises the following steps of 1, an electrode putting step: putting four electrodes in positions of the left and right side masseter muscles, musculus orbicularis oris, chin muscle groups and hyoid muscle groups at the face part of the human body; 2, a test starting step: collecting electrode signals in different activity states on the basis of the electrodes; forming the surface electromyogram including two groups of masseter muscles, musculus orbicularis oris, chin muscle groups and hyoid muscle groups; 3, an evaluation step: concretely comprising the processes of obtaining data of swallowing time limit, the average vibration amplitude and maximum collection vibration amplitude in the surface electromyogram; judging whether the surface electromyograms of the two groups of masseter muscles, musculus orbicularis oris, chin muscle groups and hyoid muscle groups are identical or not; thus forming the relevant result of the swallowing function.