The subsea pipeline plays a pivotal role in transporting offshore oil and gas, and serves as a lifeline in the offshore oil and gas production system. The local buckling and its propagation of subsea pipelines under hydrostatic pressure are the primary structural failure mode for the pipeline design. The use of ring stiffeners is an economical and effective means to improve the buckling resistance of subsea pipelines. In this paper, a Finite Element (FE) model of a pipeline with or without the ring stiffener was established in the FE software ABAQUS to systematically investigate the effects of the spacing, height and width of the ring stiffener on the ultimate buckling performance of the pipe. The simulation results including ultimate load and failure mode were subsequently compared with their corresponding testing results to validate the accuracy of the FE model. A series of parameter analyses were conducted to investigate the effects of the spacings, thickness and height of the ring stiffener on the critical buckling pressure Pcr of the pipeline strengthened with ring stiffeners, thereby proposing a formula with regard to the critical buckling pressure Pcr of the pipe with ring stiffeners. The relevant analysis results show that: 1) The effects of the spacing, thickness and height of ring stiffener were found coupled on the critical buckling pressure Pcr of pipeline, with the most significant and effective effect on the enhance of the critical buckling pressure Pcr due to closer spacing of ring stiffener; 2) An inversely increasing trend was observed for the critical buckling pressure Pcr of the pipeline with the decline in the spacing of ring stiffeners; 3) A significant effect was found on undermining the strengthening effect of the ring stiffener on critical buckling pressure Pcr of the pipe due to the presence of residual stress produced in the welding operation at the connection between ring stiffener and pipe, which indicates that the effect of residual stress should be considered in an accurate FE model of the pipe with ring stiffeners; 4) The ring stiffener with sufficient rigidity could effectively restrain the local buckling behavior of the pipe between adjacent stiffeners, and lead to a change in the buckling mode and an effective enhance in the critical buckling pressure Pcr of the pipe; 5) the critical buckling pressure Pcr of the pipeline could be accurately predicted with the proposed formula based on the above findings, an agreement that indicates that the proposed formula in this paper is appropriate as a design basis for pipes with ring stiffeners.