The oxi dation of diethyl carbonate (DEC) with O3 addi tions was studied i n an atmospheric jet stirred reactor (JSR) at 400-850K i n this work. It was seen that DEC had no low temperature reacti vity without O3 addi tion i n experi ment, while the oxi dation began from 450K with O3 addi tions. A DEC/O3 model was developed i n this work and pathway anal ysis showed that the O3 assisted l ow temperature oxi dati on of DEC came from the reaction of DEC+O i nstead of DEC+O3 . The present study i mplied that the low temperature oxi dation of DEC wi th acti ve oxygen from cathode metal oxi de might result i n the degradati on of Li-ion battery at a l ow temperature. It provi ded the first gas phase i nteraction between DEC and oxi di zi ng envi ronment by usi ng O3 as a acti ve oxygen supplier.