Recently, the pre-synthesized oil-soluble quantum dots (QDs) have triggered great interests due to advantages of monodispersity, stability and easy synthesis. Aggregation of QDs is the reason for low loading and poor efficiency during the in situ ligand exchange linker-assisted assembly process of preparing photovoltaic devices. In this work, we modify TiO2 films with 4-mercaptobenzoic acid (MBA) as linkers and adjust modification time (MT) of MBA on the surface of TiO2 films. As the MT increases from 0 to 6 min, even 360 min, loading amount of QDs and photovoltaic performance improve first and then decrease. The results of line scan in cross-sectional view of photoanodes show that QDs uniformly distribute throughout the short-MT films thickness, while obvious aggregation occur in the surface of long-MT films. The best device with 3 min of MBA modification exhibits an optimal efficiency of 5.58%.