Flexible photovoltaic devices have wide applications in many unique areas. However, the interparticle connection of photo-electrode in flexible photovoltaic devices still needs to be improved. Here, TiO2 slurries have been prepared by a three-step process, which are employed to prepare the photo-anode for flexible CuInS2 quantum dot sensitized solar cells (QDSSCs). 5 nm-sized TiO2 nanoparticles and hydrochloric acid (HCl) have been introduced in 20 nm-sized TiO2 based photo-electrodes under TiO2/HCl mass ratio of 3:1, which exhibits excellent photovoltaic performance and charge transfer property. Due to the interparticle connection enhancement by suitable content of 5 nm-sized TiO2 nanoparticles, photo-anodes with the 20/5-TiO2 nanoparticles mass ratio of 3:1 exhibits the better optical absorption property and photovoltaic performance of flexible QDSSCs. Moreover, there has maintained 98% photovoltaic conversion efficiency of flexible QDSSCs with the seriously curving condition, which can be considered the great foreground in future applications.