Membrane property decay has great effects on propylene yields when compression/condensation/membrane process is applied to recover propylene monomer. There are four types of membrane property decays. The first case is that selectivity keeping constant but membrane flux decreasing, the second case is that selectivity reducing but membrane flux unchanged, the third case is that selectivity reducing but membrane flux increasing, and the last case is that both of them all decreasing. One purpose of this paper is to judge which kind of decay leads to the separation deterioration according to the change of some parameters in the process by simulation. In order to meet target requirement, two operation parameters, membrane pressure and condensation temperature, are regulated. Results indicate that propylene yields decrease when any type of membrane property decay emerges, and the type of membrane property decay can be distinguished by the change trend of propylene yields, the variation of recycle permeate gas flow as well as propylene concentrations in permeate gas. What’s more, membrane pressure is a prior operation parameter to be regulated so as to counteract the effect of membrane property decay to some extent.