The invention discloses a control circuit for a switch converter and a control method for the switch converter. The switch converter comprises a switching circuit with at least one switching tube. The control circuit comprises a comparator circuit, a synchronous circuit, a switch-on time control circuit and a logic circuit, wherein the comparator circuit is used for generating a comparison signal on the basis of a reference signal and an output voltage of the switch converter, the synchronous circuit is coupled to the comparator circuit, and is used for generating a first synchronous signal and a second synchronous signal according to the comparison signal, the switch-on time control circuit is used for generating a switch-on duration control signal, and the logic circuit is used for generating a switch control signal according to the first synchronous signal, the second synchronous signal and the switch-on duration control signal so as to have control over switch-on and switch-off of the switching tube. Due to the fact that the synchronous circuit is used for generating the first synchronous signal and the second synchronous signal, synchronization of the comparison signal can be achieved, the delay time caused by synchronization is shortened, stability of a system is improved, and the transient response speed is ensured.