This paper studies dynamical effect mechanism of the introducing ramp compensation current on operation-state region in peak-current controlled flyback converter. The discrete iterative map model of peak-current controlled flyback converter is established based on total ampere-turns, the dynamical behaviors with the variation of the compensation current slope are analyzed, two borderline equations of the orbit states shifting are derived, and three operation-state regions of peak-current controlled flyback converter are then divided. The analysis results are verified by PSIM circuit simulations, which illustrate that the ramp compensation current not only can eliminate sub-harmonic oscillation phenomena in peak-current controlled flyback converter, but also can make its operation modes shifting from DCM to CCM.