A grayscale adjustment circuit, a driving method thereof and a display device are provided. The circuit includes: an input sub-circuit configured to output a signal of a data signal terminal to a driving sub-circuit under a control of the scanning signal terminal, the driving sub-circuit configured to store an output signal of the input sub-circuit and output a signal of the first voltage terminal to a switching control sub-circuit under a control of the output signal of the input sub-circuit, a switching time control sub-circuit configured to output a signal of each switching time signal terminal to the switching control sub-circuit under a control of each switching time control terminal, the switching control sub-circuit configured to output an output signal of the driving sub-circuit to the light-emitting sub-circuit under a control of an output signal of the switching time control sub-circuit to control the light-emitting sub-circuit to emit light.