Study the effect of the insulating layers on the liquid pipeline leakages and determining the leakage profile calculation model is critical and basic for the leakage-associated fire and explosion risk assessments for the chemical process industry. This research carried out a series of experiments, with an attempt to explore the leakage process of insulated pipeline. The experiments display that the leakage is dynamic, which is divided into three stages: initial, transitional and stable period. During the stable period, both the leak rate and pressure of insulated pipeline responding to work condition are different from those of naked pipeline. Then a fundamental formula is derived from the experimental data which is applicable for leakage calculation with insulating layers. Besides, sensitive factors that affect the leak volume are analyzed, among which the thickness of insulating layer is the most influential one. The research has designed a CFD model to reveal the dynamic leakage process in insulating layers and verify the effectiveness and accuracy of experiments. The result of this paper could improve risk assessment preciseness of liquid pipeline leakage. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.