the invention provides a method of testing reliability of a semiconductor device , wherein the semiconductor device has negative bias temperature instability nbti . the method comprises steps of : measuring a nbti curve of a first set of semiconductor devices ; measuring 1 / f noise power spectrum density and drain current at a predetermined frequency for the first set of the semiconductor devices , under a condition that the first set of the semiconductor devices are biased at a gate electric field ; measuring an equivalent oxide thickness eot of gate dielectric of the first set of the semiconductor devices ; measuring 1 / f noise power spectrum density and drain current at the predetermined frequency for a second set of semiconductor devices , under a condition that the second set of the semiconductor devices are biased at the gate electric field ; measuring an eot of gate dielectric of the second set of the semiconductor devices ; and evaluating a degradation characteristic of the second set of the semiconductor devices by using the nbti curve of a first set of the semiconductor devices . the method saves the time required for testing the reliability of a large numbers of semiconductor devices , and will not cause damages to the second set of semiconductor devices .