A control circuit and method for a buck-boost switching converter provides a mode determinative circuit to judge the timing of an operation under buck-boost mode based on the input voltage, the output voltage and the mode reference voltage; meanwhile, the control signal generating circuit is provided to turn off the second switch during the first switch being on, turn on the second switch during the first switch being off, turn off the fourth switch during the third switch being on, turn on the fourth switch during the third switch being off, wherein the duty cycles of the first and third switches are identical, and duty cycles of the second and fourth switches are identical.