Abstract: A printed circuit heat exchanger (PCHE) is a vital component of the supercritical carbon dioxide Brayton cycle (sCO₂-BC), and PCHE with zigzag channel has been massively applied because of their relatively higher heat transfer ability and easily achievable manufacturing process. Chemical etching is one of the main manufacturing processes, which also is known as the most practical microchannel forming process. Chemical etching plays an important role for the channel dimension accuracy, while the lateral etching, resulting from the isotropy of the chemical etching reaction, may cause the channel to deviate from the design dimension. The bend fillet for zigzag channel is one of the etching-induced dimension deviation, but the effect of etching-induced fillet on thermo-hydraulic performance is seldom reported. At this work, experimental measurement and CFD simulations have been performed to analyze the effect of etching-induced fillet on the thermo-hydraulic characteristics of zigzag micro-channel. Six identical test plates were etched at different manufacturing cycles, each of which has 9 channels with different inclined angles from 10 to 75 degrees and same cross-section dimension. The actual value of fillet radius is measured through a high-precision video measuring instrument, which has a precision of 2.5+Ld/100 μm. A 3D, turbulent, compressible and steady CFD simulation was conducted, and the shear-stress transport (SST) turbulence model was adopted to simulate turbulence. A first-order upwind scheme was utilized to discretize the momentum and energy equations, and the semi implicit method pressure linked equation (SIMPLE) algorithm was applied to establish the coupling of velocity and pressure. A total of 567 disturbing angle fillet radius data and 597 turning angle fillet radius data were measured and analyzed. The measurement data show that the fillet generated after chemical etching, and fillet radius decrease as a power function of channel inclined angle. Simulation results show that the fillet could smooth flow explicitly and degenerate the heat transfer inapparently. The pressure drop per unit length reduces 91.9% for model with fillet of 45° channel inclined angle, Nusselt number wound decrease 12.5% for model with fillet. Because of the relatively slight impact on channel thermo-hydraulics, turning angle fillet radius could be treated quantitatively same with that of the disturbing angle within the range of 45° inclined angle. A performance evaluation criterion (PEC), which takes into account channel heat transfer ability and flow resistant, is adopted to compare the performance of the channel with or without bend fillet. The results indicate that the compound zigzag channel with fillet provides a significant guidance of the structure optimization, and the greater the inclined angle is, the higher return gets.