We prepared low temperature phase of triple layered perovksite KCa_2Nb_3O_<10> by an ion-exchange reaction. Li-intercalated low temperature phase, Li_<0.79>KCa_2Nb_3O_<10>, shows strong diamagnetic signal around at 7.8 K. The magnetic phase transition temperature of Li-intercalated low temperature phase is higher than that of Li-intercalated high temperature phase.