By the use of the applied research cation measurement system, Fura-2 fluorescence measurement method was forwarded to detect the intracellular La³⁺ concentration, and used for investigating the transmembrane behaviors of La³⁺ to PC12 cells. An apparent dissociation constant of La³⁺-Fura-2 was 3.27×10^-11 mol·L^-1 in solutions simulating intracellular ionic composition, with pH 7.05. La³⁺ could not enter PC12 cell under the normal condition, and also could not enter the cell via the calcium channel stimulated by KCl and norpinephrine. However La³⁺ entered PC12 cell after Na⁺ within the cell were overloaded using ouabain. Amount of La³⁺ entering PC12 cell were related to both outer cellular La³⁺ concentration and intracellular overloaded Na⁺ concentration. It is suggested that La³⁺ enter the cell in Na⁺/La³⁺ exchanging mechanism.