The 35 kt/a butadiene unit of a petrochemical company uses N-methylpyrrolidone as the extraction solvent. In the NMP method for butadiene production, the control of water content in NMP plays a crucial role in the normal production of the unit. Excessive water content can easily cause poor solvent selection performance, insufficient heat source in the solvent system, and fluctuations in pressure difference in the main washing tower. This article summarizes the experience in controlling the water content in NMP solvent of the butadiene unit.