Integrity of natural gas transmission systems is of great importance for energy and environmental security. Risk of uncontrolled failure of gas pipelines by subcritical crack propagation increases due to in-bulk material degradation phenomena induced by hydrogen-assisted corrosion during their long-term service. Hydrogenation of metal during corrosion process together with working stresses facilitates a development of in-bulk damaging on nano- and microscales. It is often the main reason of decrease of pipeline steels characteristics of brittle fracture resistance under long-time operation. Therefore hydrogen assisted degradation of transport pipelines steels under operation calls for effective methods for in-laboratory accelerated degradation. The present investigation is devoted to the development of the procedure of laboratory simulation of in-service degradation of pipeline steels. The procedure of accelerated degradation of pipeline steels under the combined action of axial loading and hydrogen charging is developed and induced in the laboratory. The characteristics of the operated pipeline steels are compared with the properties of pipeline steels after accelerated degradation. This applied procedure enables, on a laboratory scale, simulating of the degradation of the pipeline steel during long-term operation under simultaneous action of hydrogenation and working loading.