The density and time constant of interface states of Au/Si3N4/n-Si (MIS) device have been analyzed by conductance method. The capacitance and conductance measurements of the device have been performed at various frequencies in the range of 1 kHz-1 MHz. Experimental results show that G(p)/omega-log(f) plots for each voltage value give a peak because of the presence of interface states. The density (N-ss) and time constant (tau) of interface states have been calculated from maximum value of the peak. The values of N-ss and tau range from 2.49x10(13) eV(-1)cm(-2) to 7.57x10(12) eV(-1)cm(-2) and from 2.67x10(-5)s to 1.67x10(-5)s, respectively.