Optical molecular imaging has been frequently used in many preclinical researches including cancer detection, tumor mechanism study, drug efficacy evaluation and targeted drug delivery. Among optical molecular imaging modalities, bioluminescence imaging and fluorescence imaging have acquired certain degree of development and attracted more and more attention in recent years for their high sensitivity and low cost. With the development of optical technology and probe technology, two-photon microscopy imaging and Raman imaging have been widely used in drug evaluation and tumor studies through cell and tissue imaging. This paper focuses on the occurrence and development of optical molecular imaging especially for its imaging method imaging system and its application in target drug delivery. Finally, the existing challenges and brand new applications of optical imaging techniques in drug delivery research are discussed.