In high-performance computing, the huge communication overhead has become one of the main bottlenecks in the improvement of its computing power, and the optimization of communication performance has always been an important challenge. For the communication optimization task, this study proposes a method based on in-network computing technology to reduce the communication overhead. In the Ethernet-based supercomputing environment, this method utilizes the RoCEv2 protocol, programmable switches, and OpenMPI to offload reduction computation to programmable switches, and it supports the two communication modes of Node and Socket. The collective communication benchmark test and the OpenFOAM application test are carried out in a real supercomputing environment. The experimental results indicate that when the number of server nodes reaches a certain scale, compared with the traditional host communication, this method shows better performance improvement in both Node and Socket modes, with the performance in the collective communication benchmark test improved by about 10%–30% and the overall application performance in the application-level test improved by about 1%–5%.