A hydrogen sensing model with subwavelength circular hole array structure based on Pd/Au composite film was proposed to detect hydrogen leakage and hydrogen concentration.Finite-difference time-domain (FDTD) method was used to simulate the subwavelength circular hole array structure with the Pd/Au composite film.The electric field energy distribution and transmission characteristics of the composite film cross and vertical section were calculated,and the extraordinary optical transmission (EOT) characteristics and sensing characteristics of the sensor structure were further analyzed under different structural parameters.The simulation results show that the subwavelength circular hole array structure with Pd/Au composite film can produce obvious EOT effect,and there are two prominent abnormal transmission peaks,denoted as peak Ⅰ and peak Ⅱ.When the hydrogen in the environment,the palladium (Pd) film will absorb hydrogen and cause the change of Pd dielectric constant,which leads to the change of EOT characteristics,especially the change of wavelength and transmittance.When the hydrogen concentration increases from 0% to 4%,the transmittance of peak Ⅰ and peak Ⅱ can reach 0.16 and 0.24,respectively.Because of the obvious change of its transmittance intensity,the hydrogen concentration can be monitored and detected by the intensity change of the transmission peak.The proposed sensor is simple to process.The thin Pd film makes the sensor respond quickly,and the EOT effect makes the signal-to-noise ratio (SNR) of the structure high.The photoelectric integration technology can be used for mass production,which has strong practical value.