Size and morphology are critical to monitoring the properties of nanocrystals. In this work, Bi₆Fe_1.9Co_0.1Ti₃O₁₈ (BFCTO) nanocrystals, which are a visible-light active photocatalyst with room temperature ferromagnetism, were successfully synthesized through a hydrothermal process. Furthermore, the morphology dependent magnetism and band gap of the BFCTO-1.00/BFCTO-1.50/BFCTO-2.00 nanocrystals are studied by adjusting the NaOH concentration to 1.00 M/1.50 M/2.00 M in the hydrothermal process, respectively. As the {117} facet ratio increases, the absorption edge has an obvious red-shift by 32 nm and the corresponding bandgap is reduced from 2.58 to 2.42 eV. Remarkably, the specific surface area normalized degradation rate of BFCTO-1.50 was considerably higher than those of BFCTO-1.00 and BFCTO-2.00 due to the optimal ratio of {001} and {117} facets.