The TAPPI T 550 standard specifies the determination method of equilibrate moisture in pulp, paper and Cardboard in chemical analysis. The standard applies to pulp, paper, Cardboard and paper products, but not to materials containing a large amount of volatile substances (except water). The test principle is to dry the sample in a drying oven at 102 ° C to constant weight, and calculate the content of equilibrate moisture in the sample by weighing. This method is mainly used for Sample Handling before chemical analysis to ensure the accuracy of the analysis results. The determination of equilibrate moisture is of great significance for the quality control of paper and Cardboard, chemical analysis and the optimization of subsequent processing technology.