A series of doping (La_0.8Ln_0.2)_2/3Ca_1/3MnO₃ (Ln represents La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, and Er, respectively) nanometer level crystals were prepared by using the sol-gel method with the same experiment conditions. It is shown that the average lattice constant and tolerance factor varies monotonically with the increase of atomic number of doping elements for the series of samples, the average lattice constant a is gradually decreased, the average lattice constant b is essentially unchanged, and the average lattice constant c is slightly reduced in general; tolerance factor t is gradually reduced in the range between 0.925 and 0.918, however with the lanthanide contraction of samples, the system remains the perovskite structure. For samples with different doping elements, there is a big discrepancy in the surface morphology and electric transport properties of samples; the distribution of each particle sizes is from 30 nm to 800nm and the transition temperature is from 82K to 194K. At zero field, the transition temperature T_c for the cerium-team (La, Ce, Pr, Nd, Sm, and Eu) doping samples does not exhibit a monotonic changes, while its behavior changes from metallic state to insulated state with the increase of atomic number; and T_c for the yttrium-team (Gd, Dy, Ho, and Er) doping samples increases with the increase of atomic number and is in accordance with the monotony of lanthanide contraction.