Abstract: In cascaded switching converter, the feedforward current ripple of the load converter can reshape the output voltage ripple of the source converter, resulting in a significant change in the stability of the source converter. Take the peak voltage ripple (PVR) controlled buck converter cascading the peak current mode (PCM) controlled boost converter as an example, the stability mechanism of the source converter in cascaded switching converter is studied. Firstly, the effect of feedforward current ripple of load converter on the stability of the source converter is shown, and the bifurcation behaviors of the source converter with the variation of the chosen circuit parameters are analyzed. Secondly, a discrete-time map model of the cascaded switching converter with three switching state sequences is established, and its Jacobi matrix in neighborhood of the fixed point is derived. Then, by detecting the eigenvalues of the Jacobi matrix, the instability mechanism of the source converter with the variation of the chosen circuit parameters is clarified. Finally, the experimental results are supplied to verify the correctness of simulation and theoretical analyses.