The application of microfluidic technology to manipulate cells or biological particles is becoming one of the rapidly growing areas in recent years. In this paper, we design three categories chip with different microstructure, including seamless, single-slit and double-slit U-type micro-trap, to evaluate the optimal structure and parameter of cell-trap microfluidic chip. Velocity control and optimization during cell transport facilitates high-quality cell capture. Numerical simulation is used to study the capture results of three U-type micro-trap different inlet velocities. By analyzing the velocity distribution of the fluid in the chip and the velocity shift of the micro-ball, the inlet velocity range of the three micro-trap structures can be determined, which are able to capture cells. The results are helpful for optimizing the structural design and get the best category with a high trapping efficiency and a good flow behavior.