A finite thickness porous wavemaker located in an infinite one dimensional channel is studied. Small amplitude waves are generated in the channel, while the equations derived from the simplified Biot's theory of poroelasticity are used within the porous wavemaker. Regular perturbation expansions, with a small parameterR, are applied. The flow-efficiency parameter,R, represents the easiness of water flow relative to the skeleton inside the porous wavemaker. The largerRis, the greater inertial reaction and the less viscous damping will be. ForRmuch less than 1, the increase of inertial reaction is greater than the decrease of viscous damping asRincreases. It is also found that the thickness of the porous wavemaker is a significant factor to the hydrodynamic pressure on the porous wavemaker when the thickness is small, but it is not a significant factor to wave profile.