The invention relates to the field of analytical chemistry and discloses a method for rapidly detecting a main component in active lime and passivated lime. The method comprises the following steps: 1, weighing a proper amount of active lime and passivated lime samples and carrying out a blank test along with the samples; placing the samples into a heating container; adding a proper amount of hydrochloric acid solution; heating till the samples are completely decomposed; cooling a few undissolved substances of the passivated lime sample to the room temperature; after the solution is filled into a volumetric flask to fix volume, respectively extracting two parts of proper amount of test solution; and 2, respectively titrating calcium oxide and magnesium oxide or calcium and magnesium. Theinvention has the characteristics that the sample decomposition is simplified, and a measurement error is reduced and the analysis time is shortened by controlling the titer of EDTA and EGTA titrand within the burette volume range; two separately added indicating agents are prepared into a mixed indicating agent to be added once when the calcium and magnesium or magnesium oxide is directly titrated so as to reduce the operation time; and the final result is obtained by adding the experience correction coefficient in the passivated lime sample.