Novel homojunction TiO2 samples of anatase TiO2 nanoparticles with dominant {101} facets (TP) supported on anatase TiO2 nanosheets with dominant {001} facets (TS) in different ratio of TP/TS (denoted as R%TP/TS) were prepared by a vapor-induced hydrothermal method and followed by photothermocatalytic treatment. The TiO2 samples were characterized with TEM, XRD, Raman, XPS, BET, PL spectra, UV-vis absorption spectra, photo-current measurement, and fluorescence emission decay. It is found that the formation of the TP/TS homojunction significantly enhances the photocatalytic activity for acetone photodegradation. The TiO2 samples of 2.5%TP/TS, 5%TP/TS, and 10%TP/TS exhibit much higher photocatalytic activity than TS and TP. Especially, the specific CO2 production rate for acetone degradation of the optimized 5%TP/TS is 4.0, 5.4 and 3.3 times higher than that of TS, TP, and P25, respectively. The results of photocurrent, PL, and fluorescence emission decay demonstrate that the significant enhancement in photocatalytic activity is attributed to the efficient improvement in photogenerated electron-hole separation efficiency by forming homojunction. This study provides a new approach by building homojunction to significantly enhancing the separation efficiency of the photogenerated electron-hole and photocatalytic activity.