Mesoporous slabstone‐like anatase TiO2 micro‐nanometer composite structure has been successfully synthesized by a facile solvothermal method at 180 °C using polyethylene glycol (PEG) as a structure‐directing agent, followed by calcination at 400 °C for 2 h. The crystal structure and morphology of the product were characterized by XRD, SEM, TEM and HRTEM. Its BET specific surface area was obtained from N2 adsorption‐desorption isotherm measurement. Rhodamine B (RB) aqueous solution was used to evaluate the photocatalytic activity of the as‐prepared TiO2 under simulated sunlight irradiation and compared with that of commercial TiO2 (P25). A RB and methyl orange (MO) coexisting solution was chosen to investigate the photodegradation preference of the slabstone‐like TiO2 on these two dyes. The results show that the photocatalytic activity of the as‐prepared TiO2 is much higher than that of P25, and MO is the preferential degradation species in the MO‐RB mixture solution.