Flame ionized detector has been such widely applied in chemical analysis since its great invention and the discovery of chem-ionization. Thanks to the excellent contribution of Sternberg and the successors in this field, effective carbon number concept (ECN) can make the analysis calibration greatly simplified especially when authentic standard substances are unavailable or in the complicated case such as petrochemical industry and biomass processing. To supplement the ECN rule in multi-ethers, this work determined relative response factors of poly(oxymethylene) dimethyl ethers experimentally, and developed a probabilistic P₁-P₂ effective carbon number model (P-ECN) for multi-ethers compounds. Results showed this method could improve the precision of quantitative analysis for poly(oxymethylene) dimethyl ethers and could predict relative response factors of other ethers with similar structure to a degree. LOD for each DMM_n monomer ranged between 0.4-0.7ng, and MDL ranged between 2-4 ug/mL. In the practical quantitation of diluted samples at level of 10ug/mL, the relative standard deviation was less than 5%. Practical ethers-fuel blend with complex composition also was quantified with errors less than 3%.