Abstract: When a free span of submarine pipeline appears, the load on the pipeline is increased, so the pipeline is easily subjected to damage. In this paper, the spanning mechanism of submarine pipeline was analyzed briefly based on the characteristics of free spanning submarine pipeline. Then, the damage mechanism of gravity, buoyancy, wave force and current force on the free span and their research status were summarized. Finally, the development trend of the study on free span pipelines was prospected. It is indicated that the study direction on the free span of submarine pipeline is mainly concentrated on analyzing the deformation and damage of submarine pipelines with different structural forms under the joint effect of complex loads. In the future, it is necessary to investigate systematically the influencing rules of flow field properties and ground motion characteristics on the flow field and stress around the pipeline, calculate the allowable spanning length of free spanning submarine pipeline under more complicated constraints, compare the allowable span lengths of free spanning submarine pipeline according to different criteria and determine the applicability range of each criterion.