Receiver of communication system and eye diagram measuring method

An eye diagram measuring method is provided, including: sampling, according to a reference voltage and a reference clock, a compensated input signal to obtain a first sampling result; and sampling, according to a scan voltage and a scan clock, a to-be-compensated input signal to obtain a second sampling result, including: (b1) storing a minimum phase and a voltage level which cause the first sampling result to be the same as the second sampling result; (b2) increasing the voltage level and repeating step (b1); (b3) decreasing the voltage level and repeating step (b1); (b4) storing a maximum phase and the voltage level which cause the first sampling result to be the same as the second sampling result; (b5) increasing the voltage level and repeating step (b4); and (b6) decreasing the voltage level and repeating step (b4). Voltage levels, maximum phases and minimum phases which are stored are for adjusting the reference voltage and the reference clock.