The work aims to study the selection method and technical indicators of the sealing of envelop materials for military equipment under field conditions, and provide the technical basis for guiding the selection of envelop materials. Firstly, according to the military service requirements, the technical indicators of envelop materials were determined, and then based on the related technical testing standard, the method used to test envelop materials was determined. Secondly, a one-year field exposure test was conducted in typical climatic conditions, and a third-party auditor was entrusted to conduct technical testing on the properties of envelop materials before and after the test. Finally, according to the test results, the envelop materials that met the requirements were selected. After the field exposure test and the third-party technical testing of the 9 newly developed envelop material samples, 3 envelop materials that met the requirements of technical indicators were selected. The proposed selection method and technical indicators of envelop materials are reasonable and feasible, and the selected envelop materials have good performance and are suitable for field sealing and protection of military equipment, which is conducive to improving the readiness rate of military equipment.