A receiver having a first clock signal is provided. The first frequency of the first clock signal is adjusted to be close to a second frequency of a second clock signal of a transmitter. The receiver includes a clock generator, a processor and a controller. The clock generator is for generating the first clock signal. The processor is for outputting a first control signal to control the clock generator to adjust the first frequency to be close to the second frequency when an absolute value of a current difference between the first and the second frequencies at a current time point is larger than a threshold. The controller is for outputting a second control signal to control the clock generator when the absolute value of the current difference is smaller than the threshold, so as to reduce the load of the processor.