It is very important to accurately predict the strain of dented pipelines accurately for the safety evaluation of pipelines in service with dent defect. However, the strain prediction formula of dented pipe in existing American Society of Mechanical Engineering (ASME) standard neglects the influence of internal pressure on the strain of pipe. Therefore, a finite element model of dented pipe was established in this paper with internal pressure load, and studies the influence of indenter radius, material property, pipe internal pressure, pipe wall thickness and pipe diameter on the maximum equivalent plastic strain (ε0max) of the pipe at different dent depths, a strain prediction model for pipelines in service with dent defect is proposed. The results show that when the relative dent defect depth is 6%, the internal pressure of the pipeline increases from 0 MPa to 8 MPa, and the ε0max increase rate is 50.26 %. The average error of ε0max prediction model is 5.32 % compared with the result of the finite element model. The maximum error and minimum error are 12.51% and4.74 % compared with the result of test results in the literature. The prediction model provides some reference for safety evaluation of pipeline in service.