The new amino acid complex nanoparticles of bismuth and leucine can be prepared very easily by a room temperature solid-solid reaction. The various characterizations indicate that the formula of the complex is BiCl[(CH(3))(2)CHCH(2)CHNH(2)COO](2)1.5H(2)O. The crystal structure of the solid complex belongs to monoclinic system with the lattice parameters: a = 1.6036 nm, b = 1.9903 nm, c = 2.1979 nm and beta=108.06 degrees . The new solid complex is nanoparticles with average size about 80 nm.