Abstract: It is important to study the hidden structures of material transport in marine fluids to understand the material transport process. Therefore, this study uses the four-particle RD approach to detect the material transport structure hidden in the time-varying double gyre ideal flow field and the flow field in Haizhou bay, and the material transport processes in these fields are simulated by Regional Ocean Modelling System (ROMS) and particle tracking model. The results indicate that the four-particle RD approach effectively identifies structures such as material mixing barriers and material aggregation zones in the nearshore flow fields, offering macroscopic insights into predicting trends in material transport. The application of the four-particle RD approach in Haizhou bay reveals the presence of clockwise helical forward RD structures in the shoal areas outside the Guanhe River estuary. These structures form material transport barriers or channels that impede or accelerate the material transport process.