A control method for a DC/DC converter and a DC/DC converter are provided. The method includes: detecting an input voltage and an output voltage, and calculating a voltage gain according to a ratio of the output voltage to the input voltage; determining an operating mode of the DC/DC converter according to a first threshold and the voltage gain, and setting a first duty ratio and a second duty ratio according to the mode; detecting an inductor current to generate a current feedback signal, and then setting a regulation component according to the current feedback signal; regulating the first or second duty ratio according to the regulation component and generating driving signals to control the two groups of switches. The converter could operate in the Buck mode, Boost mode and Buck-Boost mode, and the voltage gain could be linearly continuous around 1.