Flexible mattress for bed protection of estuary regulation structure may produce deformation when the river bed nearby regulation structures encounters erosion. It plays an important role to find out the deformation conditions and position of original flexible mattress in safety and stability of regulation structure and the rectification effect of the estuary. Taking the detection of flexible mattress for bed protection in New Liuhesha beach protection project as an example, and through the detection scheme design and field inspection, we obtain the comprehensive detection technology of flexible mattress for bed protection under complex condition of high turbidity estuary. It provides a basis for the follow-up work. It not only meets the engineering need but also provides reference for similar work in the future.