This work, surface fluorination process was used for improvement photocatalytic activity of TiO2. Photocatalytic activity was observed by degradation of methylene blue (MB). TiO2 nanopowders were prepared by sol-gel technique from titanium-tetraisopropoxide (TTIP): 2-propanal (2-PP) with the ratios of 1:5, 1:15, and 1:30 (V/V) then adjusted pH by nitric acid at 2. The result showed that grain size of TiO2 powder decreased as 2-PP ratio increase. The grain sizes of TiO2 were in the range of 14-25 nm. Photocatalytic activity was considered by characteristic time constant (τ). The results showed that F-TiO2 presented higher photo-degradation than naked TiO2. At 1:30 for TTIP: 2-PP ratio with improvement by surface fluorination (F-TiO2) could degrade MB faster than other samples under weak-UV at irradiation time of 1 hr. The 1:30 sample degraded MB reach to 96%. The results led to conclude that surface fluorination is the good process to improve photocatalytic activity for TiO2. © (2014) Trans Tech Publications, Switzerland.