We present a statistical study on the acceleration of CMEs. This study is based on 23 CME events best observed by SOHO LASCO/C1 coronagraph, which observes the inner corona from 1.1 to 3.0 $R_S$. The kinematic evolution of a CME has a distinct acceleration phase that mainly takes place in the inner corona. We find that the acceleration duration distribution ranges from 10 to 1100 min with a median (average) value at 54 min (169 min). The acceleration magnitude distribution ranges from 6 m s$^{-2}$ to 947 m s$^{-2}$ with a median (average) value at 209 m s$^{-2}$ (280 m s$^{-2}$). We also find a good correlation between CME acceleration magnitude A (in unit of m s$^{-2}$) and acceleration duration T (in unit of min), which can be simply described as A=10000/T.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html