Water content of the oil production of oil field development is relatively important parameters; it is calculating the comprehensive water cut oil field, and an important basis of evaluation of development effect. Because the water content of oil well an item is all oilfield laboratories must analyze project, which is the detection project throughout the whole process of oilfield development, that is the typical and representative, preparation of crude oil moisture detection comparison samples of oil base laboratories, can effectively inspect the grass-roots laboratory test ability and analytical testing level, make each laboratory to strictly enforce the standards, issued by the inspection data onto high accuracy and comparability, meet the test oil company in the production process testing requirements. At the same time on the primary laboratory comparison samples test data dispersion is analyzed, so that the data can greatly improve the comparability. This paper introduces how to prepare comparison samples, and through the sample test data dispersion analysis, considers that the scientific method of reducing the data divergence is unified testing standards, unified operation equipment, unified using medicament, unified operation method.