Cancer has become the leading cause of human death worldwide. There are many challenges in the treatment of cancer and the rapidly developing area of nanotechnology has shown great potential to open a new era in cancer therapy. This article, rather than being exhaustive, focuses on the striking progress in the drug delivery nanosystems (DDNS) for cancer therapy and selects typical examples to point out the emerging mode of action of DDNS from our perspective. Among the outstanding advances in DDNS for cancer therapy is the development of “multicomponent delivery systems”, “multifunctional nanocarriers” and “multistage delivery systems”. However, these represent only one aspect of DDNS research. In addition, nature is the best teacher and natural evolution pressure has meant that virions conform to the “multitarget, multistage and multicomponent” (3M) mode of action. Amazingly, traditional Chinese medicine (TCM), used for over 4000 years in China, also displays the same mode of action. Integrating the previous notable progress in nanoparticle technology, learned from the building mode of natural virions and the action concept of TCM, we propose an integrity-based 3M mode DDNS for cancer therapy: multitarget, multistage and multicomponent, which are not fragmented parts but an interconnected integrity. Based on the physiological multitarget and the pharmacokinetic multistage, multicomponent DDNS are rationally designed, where different components with individual specific functions act in a synergistic manner against each target at each disposition stage to maximize the targeted delivery effectiveness. In this article, we introduce each component of 3M DDNS in detail and describe some typical cases to realize the tumor-homing purposes.