The invention discloses a method for measuring the bicarbonate ion utilizing capability of a plant. The method comprises the following steps of: (1) respectively measuring stable carbon isotope compositions, i.e. delta 13C values of leaves of a plant to be studied and a reference plant; (2) measuring the stable carbon isotope composition, i.e. delta 13C value of microalgae; (3) substituting the delta 13C value of the leaves of the plant to be studied, the delta 13C value of the leaves of the reference plant and the delta 13C value of the microalgae into a two-end-member model and calculating the proportional share of bicarbonate ions utilized by the plant to be studied in an inorganic carbon source; (4) measuring the net photosynthetic rate of the leaves of the plant to be studied; and (5) deriving the bicarbonate ion utilizing capability of the plant to be studied according to the net photosynthetic rate of the leaves of the plant to be studied and the proportional share of the bicarbonate ions utilized by the plant to be studied in the inorganic carbon source. The invention can be used for quantitatively measuring the bicarbonate ion utilizing capability of the plant with less plant materials and less steps and simple calculation.