Observation of cloud base height (CBH) is crucial in modeling earthatmosphere radiation budget and for the aviation safety. CBH is estimated by combining measurements from CloudSat/CALIPSO and MODIS based on the International Satellite Cloud Climatology Project (ISCCP) cloudtype classification and a weighted distance algorithm. The proposed method is validated by ATrain data. The result indicates that the mean error of CBH is always less than 3 km, while the average error of CBH of low clouds is smaller than 1 km. The difference between the real and estimated CBHs is mainly within 1 km when distance ranges from 0 km to 500 km, and the root mean square error is smaller than 3 km. Application to the 3D cloud structure of a frontal cloud is also demonstrated.