The invention provides a micro-
oxygen purifying method used for removing harmful gas in 
yellow phosphorus tail gas, which is characterized in that 
mixed gas containing HCN, PH, H2S, COS and CS2, with the speed of 1000-5000 / h is heated to 150-200 DEG C by a 
heat exchanger and sent to a 
catalytic hydrolysis reactor; more than 90% of HCN and 85% of COS and CS2 can be respectively hydrolysed as NH3, CO, H2S and CO2; subsequently, the 
mixed gas enters a 
selective catalytic oxidation reaction; PH3 and H2S are catalysed and oxidated as P2O5 and S; harmful gas in the 
mixed gas which is disposed twice is removed further in a fine decyanation reactor and the 
sulfide thereof is removed by a fine desulfurization reactor; NH3 is selectively catalysed and oxidated as N2, thus purifying the mixed gas. The method of the invention leads the violent toxic matter to be converted into non-toxic matter, generates no secondary 
pollution, recovers the outgrowth sulphur, improves the utilization ratio of the resource, eliminates the environmental 
pollution due to 
waste gas exhausting, and has the advantages of simple process, few investment and low running expense.