In this work, HNbxTa1-xWO6 (x=0, 0.3, 0.5, 1) nanosheets were successfully synthesized by an in-suit doping strategy at the molecular level and an exfoliation-restacking process. The crystal phase structures, surface morphologies, and chemical components of the obtained HNbxTa1-xWO6 nanosheets were systematically characterized by X-ray diffraction patterns, laser Raman spectroscopy, scanning electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy and N2 adsorption-desorption measurements. The adsorption and photocatalytic degradation of RhB aqueous solution under dark and simulated sunlight irradiation were investigated, respectively. The adsorption results demonstrated that the large total pore volume and strong acidity are favorable for the adsorption of RhB, and the photocatalytic results showed that the introduction of Ta element greatly improved the photocatalytic activities of the as-prepared HNbxTa1-xWO6 nanosheets. Among the HNbxTa1-xWO6 nanosheets, HTaWO6 nanosheet has the highest photocatalytic activity for RhB degradation with a rate constant of 1.62×10−2 min−1. According to the photocatalytic result, it can be concluded that the use of in-suit doping to control the energy band structure is an effective method for designing efficient photocatalysts.