Abstract: Paralysis outbreak due to flour contaminated with Triorthocresyl phosphate(TOCP) occured in suburban of Xi'an city in 1995.At tack rate was 6.0465‰.Hong-Guang village′s was the highest 26.3566‰ among 5 villages.The attack rate of the second villager group was also higher among 3 villager groups of Hong-Guang village.Incubation period was 94 days at most, 40 days at least and average was 64 days.There were 2 peaks during outbreak.Majority cases was childhood and adults.Gender ratio was 1:1.12.The TOCP paralysis had clearly family aggregation χ2 =11.23, P<0.05.Aft er high risk factors were analysised on statistics, it was confirmed that high risk fact or was flour which was contaminated by TOCP.Also TOCP was checked out from flour and other samples in epidemic zone by useing TCL and Gas Chromatograph.According to epidemiology, clinical medicine and laboratory study, it is confirmed that TOCP was aetiology of the paralysis outbreak.