Titanium thin films have been prepared on borosilicate glass (BK7) substrates by ion beam sputtering technique with different voltage of sputtering, and the effect of energy process on the surface morphology is studied with the help of atomic force microscopy (AFM). Numerical correlated calculations show that the surface morphology appears to be fractal under these deposition conditions. Based on the fitting of height-height correlation functions of thin films to the phenomenological formula of fractal surface, the parameters such as fractal dimension, lateral correlation length and interface width are all obtained. The results show that the interface width increases but the fractal dimension decreases with the energy of incident Ar ions when the voltage of the sputtering is between 300 V and 700 V. Furthermore, the growth mechanism is studied based on the obtained fractal dimension under the different voltage of sputtering.