[en] Research on organic phase loss routes of extraction and re-extraction process to a uranium-molybdenum associated ore indicate that loss routes include organic phase entrained by aqueous phase and interfacial crud, volatilization and dissolution loss of organic phase, organic phase loss from negative pressure ventilation system which is the main route of organic phase loss. Recommended ways to reduce organic phase loss are: setting up static sealed pool for aqueous phase, separating organic phase from interfacial crud by centrifuge, the whole airtight utilization process of organic phase. Trough extractor with negative pressure ventilation system is airtight, and the negative pressure is minus 2000 Pa generated from induced draught valve installed on the by-path ventilating duct. The vents is installed at the far end of mixer-settler. Temperature of extraction and re-extraction is ≤30 ℃, and altitude difference of extraction liquid level and trough extractor roof is > 8 cm. Based on the control methods, the organic phase loss of ton ore is decreased to 2.5 kg. (authors)