Molecular imaging enables noninvasive characterization, quantification and visualization of biological and pathological processes in vivo at cellular and molecular level. It plays an important role in drug discovery and development. The skillful use of molecular imaging can provide unique insights into disease processes, which greatly aid in identifications of target. Importantly, molecular imaging is widely applied in the pharmacodynamics study to provide earlier endpoints during the preclinical drug development process, since it can be applied to monitor the effects of treatment in vivo with the use of biomarkers. Herein, we reviewed the application of molecular imaging technologies in antitumor drug development process ranging from identification of targets to evaluation of therapeutic effect.