Eye diagram scan circuit and associated method for a receiver circuit, including a level adjust circuit, a phase interpolator and a control module. The receiver circuit provides a first data signal and a primary phase data according to a received signal. The control module provides a phase offset data and a level offset data. The level adjust circuit adjusts a level of the received signal in respond to the level offset data; the phase interpolator triggers according to a sum of the phase offset data and the primary phase data, so a second data signal is provide in response to the level-adjusted received signal. The control module compares the first data signal and the second data signal, and accordingly provides an eye diagram scan result for the phase offset data and the level offset data.