Abstract: In order to determine the concentration of cobalt and phosphorus in the organic phase of hydroformylation reaction, the sampling system of inductively coupled plasma mass spectrometer (ICP-MS) has been modified to allow direct analysis of the organic phase. The solvent was diluted online and the element contents were conveniently determined by direct injection of sample. The online dilution ratios were modulated by parameters calibration of the sampling pumps. The results error between the online and manual dilution was less than 3%. Based on the above improvements, ICP-MS can timely monitor the concentration of cobalt and phosphorus in the hydroformylation reaction process, thus identify the problem of insufficient production capacity and guide the specific response plan to increase productivity in the industrial hydroformylation.