Water content is an extremely important indicator for lubricating oil, and this technical parameter greatly affects the quality and performance of lubricating oil. In order to more accurately detect the water content index parameters in lubricating oil, this article first builds an experimental platform and improves the detection accuracy of water content values on the basis of high-precision standard temperature and humidity sensors; at the same time, the influence of factors such as oil viscosity, oil brand, and different oil usage scenarios on the solubility of water in lubricating oil was verified. A method for calibrating the solubility value of lubricating oil for different usage levels and functions was provided, thus achieving accurate online monitoring of the water content index parameters of lubricating oil.