To explore the effect of the isomeric organic ligand on the helical structure, herein, three Wells–Dawson polyoxometalates (POMs) based hybrid compounds with different helical structures by using the isomeric pyttz organic ligands, [Ag5(pyttz-I)3(H2O)2(HP2W18O62)]·H2O (1), [Ag10(pyttz-II)6(trz)2(H2O)6][HP2W18O62]2·8H2O (2), and K2[Ag7(pyttz-III)4][P2W18O62]·2H2O (3), were successfully isolated. Compound 1 shows a three-dimensional (3D) inorganic framework constructed by three kinds of pure inorganic helical chains and steadied by organic molecules, and so does compound 2, but the 3D framework is constructed by two types of organic–inorganic hybrid helical chains. Note that compound 3 shows a two-dimensional layer with one kind of organic–inorganic hybrid helical chain. The influences of the organic ligand on helical structures of the new compounds have been reported. In addition, the photocatalytic results of three new compounds for the photodecomposition of MB indicate Wells–Dawson POMs based hybrid compounds are one kind of good photocatalyst to some dye pollutants.