  The proposed Circular Electron Positron Collider (CEPC) imposes new
challenges for the vertex detector in terms of pixel size and material budget.
A Monolithic Active Pixel Sensor (MAPS) prototype called TaichuPix, based on a
column drain readout architecture, has been developed to address the need for
high spatial resolution. In order to evaluate the performance of the
TaichuPix-3 chips, a beam test was carried out at DESY II TB21 in December
2022. Meanwhile, the Data Acquisition (DAQ) for a muti-plane configuration was
tested during the beam test. This work presents the characterization of the
TaichuPix-3 chips with two different processes, including cluster size, spatial
resolution, and detection efficiency. The analysis results indicate the spatial
resolution better than 5 $\mu m$ and the detection efficiency exceeds 99.5 %
for both TaichuPix-3 chips with the two different processes.
