The invention discloses a method for determining the content of rhodium in a water-soluble rhodium-phosphine complex. The method is easy to operate, and the determination result can be taken as the commercial evaluation on the content of rhodium in a finished catalyst product. The method includes the steps of: (1) taking a sample, adding concentrated sulfuric acid to conduct digestion; (2) adding concentrated nitric acid dropwise to drive out excess sulfuric acid; (3) adding hydrochloric acid dropwise to drive out nitric acid; (4) conducting dilution; (5) adding sodium nitrite; (6) adding a saturated solution of nitrate cobaltic hexamine dropwise till no precipitation of yellow sediment; (7) ageing the sediment for 10-30min; (8) washing the sediment with a 0.05% nitrate cobaltic hexamine solution twice, with anhydrous ethanol 3 times, and with ethyl ether once in order; (9) performing weighing; and (10) calculating the content of rhodium according to the formula as shown in the specification, wherein w1 is the sediment weight, w2 is the crucible weight, w is the sample weight, and 0.19054 is the conversion factor of a rhodium double salt to rhodium.