Micro/mesoscale metal sheet hydroforming (SHF) process is an efficient approach suitable for mass production to fabricate metal parts with micro/mesochannel features. In conventional sheet hydroforming process, the channel’s feature sizes (e.g., the channel width, fillet radius, etc.) are much greater than the sheet’s thickness, so that the influence of the fillet and the inhomogeneous stress/strain distribution through the thickness direction can be ignored. However, the influence becomes increasingly important, because the thickness of the sheet and the feature dimensions of the microchannel are in the same magnitude as the feature sizes of the material and tools reduced to micro/mesoscale. In this paper, an analytical model with consideration of the inhomogeneous stress/strain distribution was developed to predict the channel profile at different pressures in micro/mesohydroforming process. Plane-strain deformation behaviors in the section of the workpiece were studied, and the relation function between the pressure and the channel height was established. Via this function, the channel height could be accurately predicted for a given pressure. Furthermore, an experimental setup was prepared, hydroforming experiments using microchannel dies with various geometric dimensions were conducted, and the channel height of the workpieces was measured. It was found that the experimental results matched well with the simulation results, which confirmed the validity of the analytical model proposed in this study. It is expected that the model will be beneficial in the optimization of the microchannel hydroforming process.