Abstract: An improved 3D finite-difference time-domain(3D-FDTD)method based on the lossy Drude dispersive modals is presented.The extraordinary transmission characteristics of subwavelength hole array are investingated by using the dispersive FDTD method.The influences of the thickness of film,the hole size,the refractive index of substrate,the refractive index of filled medium,the periodic of arrays on the characters of transmission spectra are simulated.It is found that increasing the hole size results a higher transmission,and transmittance decreases as the periodic of array increases.The transmission can enhanced by filling the holes with higher refractive index medium.