R1234yf has attracted wide attention because of its excellent environmental protection performance. However, the potential flammability hazards of R1234yf will affect its use and promotion. This article will focus on the flammability changes of R1234yf before and after adding different flame retardants. Firstly, the flammability limits of the mixtures of R1234yf+R13I1 and R1234yf+N 2 were tested out. And the critical suppression ratios of the two flame retardants/R1234yf were obtained by analyzing the experimental data. The chemical inhibition mechanism of R13I1 to R1234yf was analyzed, and a brief mechanism for chemical inhibition of flame retardants was obtained from two stages. Then, in order to more reasonably determine the inhibiting characteristics of flame retardants to flammable refrigerants, a method for evaluating the inhibition properties of flame retardants with three parameters was proposed, including critical suppression ratio, flammability limits range, and inhibition efficiency. And the inhibition characteristics of four flame retardants R13I1, N-2, R134a and R227ea on R1234yf were obtained, respectively. Finally, the global warming potential and flammability limits (or critical suppression ratios) of three mixtures were compared based on a new two-coordinate schematic diagram, which can comprehensively compare the environmental protection and safety of binary mixtures. The results will provide references for reducing the combustibility hazards of R1234yf and searching for new refrigerants. (C) 2020 Elsevier Ltd and IIR. All rights reserved.