Four new neodymium(III) coordination polymers, Nd(HL)2(CH3COO) (1), Nd(HL)2(CH3COO) (1′), Nd(HL)2(C2H5COO) (2) and Nd(HL)3(H2O) · 4H2O (3) were prepared by the hydrothermal reactions of Nd2O3 with 1,6-dihydro-6-oxopyridine-3-carboxylic acid (H2L) using the modulation roles of different carboxylic acids (acetic acid, malonic acid, propionic acid and formic acid for 1, 1′, 2 and 3, respectively). Complexes 1 and 1′ are conformational polymorphs: 1 crystallizes in an acentric space groupCmc2(1) and shows a new 3D {3,6} topology (63)2(4261083), while 1′ crystallizes in the centrosymmetric space groupPbcn, exhibiting the rutile topology. Complex 2 possesses the same space group and topology as 1′. Complex 3 exhibits a new 2D three-node network topology with the Schläfli symbol of (83). Complex 1 is a second-order nonlinear optical molecular material, and magnet measurements indicated the magnetic coupling interaction between Nd3+ ions in these four complexes is weak.