During gravel packing operations in offshore oilfields, incomplete packing or packing failure may occur due to design, irregular borehole, formation, and other reasons, which has a great impact on the production of oil wells. A new type of multi?channel bypass screen is designed and developed. After conventional packing is completed, the gap section continues to be packed through the bypass channel. The performance of the designed multi?channel bypass screen is evaluated with a self?developed large full?scale horizontal well gravel packing test simulation system, and the following conclusions were obtained through experiments. In the gravel packing experiment through the bypass pipe without a sand bridge, the packing efficiency of the bypass section measured is 100.0%. When the glass conveying pipe is connected, the ratio of the return flow rate at the outlet to that of the glass conveying pipe is 0.68 : 1. The liquid flow rate in the bypass channel is greatly improved compared to that in the unpacked clean water experiment.The packing efficiency of the gravel packing test through the bypass pipe with a sand bridge is 62.5% higher than that of the conventional screen. The ratio of the return flow rate at the outlet to that of the glass conveying pipe is 1.60 : 1.The experiments show that the new screen has favorable bypass performance and conveying performance and high gravel packing efficiency.