Abstract: Inaccurate measurement of the mean temperature of petroleum and its liquid products stored in a tank results in low measuring precision of the liquid volume. Therefore, based on the requirement of tank volume.for temperature measurement, the paper introduces the structure of mean temperature sensor of copper thermoresister, and gives the way to improve precision according to theoretical analysis. The performances of tensile and compression strains are studied by experiments. By comparing the results from inspection with that from tests and user application. It is proved feasible to constitute mean temperature by elongating industrial copper thermoresister. The systematic precision achieved is better than ±0. 25 ℃.which is of the international level.