The anomalous chemical wave propagation of an unstirred Belousov-Zhabotinsky (BZ) reaction was observed under exposure to a gradient static magnetic field (SMF). The gradient SMF effect on the BZ reaction was investigated by increasing the thickness of the BZ medium up to 0.9 mm under the conditions of the extremely reduced water evaporation and surface tension caused by air-water interfaces. The respective maximum values of magnetic flux density (B(max)), magnetic flux gradient (G(max)), and the magnetic force product of the magnetic flux density x its gradient (a magnetic force parameter) are 0.206 T, 37 T m(-1), and 4 T(2) m(-1). The experiments demonstrate that the more increased thickness of the BZ medium induces the larger anomalous wave propagation toward the peak magnetic gradient line but not toward the peak magnetic force product line. The anomalies were significantly enhanced by the increased thickness of the BZ medium at the shorter distance from the maximum magnetic gradient point. The possible mechanism of SMF-induced anomalous wave propagation related to the BZ medium thickness is that the micro-magneto-convection-induced flow of the paramagnetic iron ion complexes at the wavefronts can be accelerated by increases in both the spatial magnetic gradient and the volumetric depth of the diffusion layer.