A control method used in a four-switch buck-boost converter includes: sensing the output voltage and generating a feedback signal; generating a compensation signal based on a reference signal and the feedback signal; sensing the current flowing through the inductor and generating a current sensing signal; comparing the current sensing signal with the compensation signal; turning on the first and third transistors and turning off the second and fourth transistors when the current sensing signal reduces to be lower than the compensation signal; turning off the first transistor and turning on the second transistor when the on-time of the first transistor in one switching period reaches a first time threshold; and turning off the third transistor and turning on the fourth transistor when the on-time of the third transistor reaches a second time threshold.