Abstract: A method for determining a signal quality includes: receiving a signal from a circuit device; generating multiple eye diagrams according to the signal; determining whether each eye diagram is normal according to a basic index to generate a first determination result, wherein the basic index comprises an eye height and an eye width; in response to the first determination result indicating that each diagram is normal, determining whether each eye diagram is normal according to an advanced index to generate a second determination result, wherein the advanced index comprises at least one of a combination of an area and a contour length, a combination of a density and a gradient, and a combination of multiple slopes; and in response to the second determination result indicating that each eye diagram is normal, determining the signal quality of the signal according to each of the multiple eye diagrams.