Objective To analyze the pathogenic substance, cause of pollution, cause of unidentified food contamination of 278 outbreaks of unexplained foodborne disease, offer suggestions and provide reference for identifying the pathogenic substances. Methods The data of unexplained foodborne disease outbreaks between 2010-2016 from Foodborne Disease Outbreak Surveillance System was collected, and then sorted and analyzed with Microsoft Excel software. Results A total of 436 foodborne disease outbreaks were reported in Shanxi province from 2010-2016, among which 278(63.76%) were unexplained foodborne disease. These 278 events, with less than 100 patients each, all were general food safety accidents. 40.65%(113/278)of the events occurred in the third quarter. The symptoms of digestive system were the major clinical situation, and 74.76%(1 303/1 743)cases had with abdominal pain. The most common setting was catering service establishment (49.64%,138/278). 30.51%(83/272)of the events collected samples, while only 2.90%(4/138)collected all four types of samples(including food samples, patients' biological specimens, employees' biological specimens and environmental samples) in catering service establishment.There were 137 events occurring after people eating together many times, among which only 18.25%(25/137)investigated the multiple meals,16.79%(23/137)investigated unaffected person after sharing the same suspicious meals, and only one event carried on the analytical research. There were 138 events occurring in catering service establishment, among which only 54.35%(75/138)carried out investigations of food hygiene, but not comprehensive. Conclusion There were many events with unidentified pathogenic substance, unidentified cause of pollution, unidentified contaminated food as well as unidentified triggering link. The reasons for this included imperfect investigation mechanism, outdated diagnostic criteria, insufficient inspection equipment and ability, absent of qualification of food inspection, nonstandard sample collection, inadequate epidemiological investigation, administrative intervention as well as the influence of social factors.