The iterative mapping model of current-mode Buck-Boost converter was deduced.On the basis of the model,bifurcation phenomena were studied with input voltage,reference current and load resistance as variable parameters.Bifurcation diagrams were obtained by Matlab simulation,and it can be seen from the figures the effects of bifurcation parameters on system states.In designs,optimal parameters may be chosen in the light of the rules summarized in the paper.