An adjusting mechanism, adaptive to a main body of a centrifugal compressor, comprises a diffuser channel width adjusting assembly and a gas bypass assembly. The diffuser channel width adjusting assembly comprises a width adjusting annular plate and a first valve stem. The width adjusting annular plate is movably disposed in a diffuser channel of the main body. The first valve stem is connected to the width adjusting annular plate, and configured for driving the width adjusting annular plate to move to adjust the width of the diffuser channel. The gas bypass assembly comprises a gas bypass valve and a second valve stem. The gas bypass valve is movably disposed in a gas bypass passage of the main body. The second valve stem is connected to the gas bypass valve, and configured for driving the gas bypass valve to move to adjust the opening of the gas bypass port.