Abstract: New drugs approved by authorities are classified into two categories: new molecular entities (NME) and fixed dose combination (FDC) formulations, both of which are documented by scientific experiments and clinical trials. Complex diseases frequently possess multifactorial causes, and drugs that only focus on a single target may not achieve satisfactory results; moreover, it is difficult to achieve full optimization of the pharmacodynamics, pharmacokinetics, safety, and patient compliance for a drug. Therefore, combinatorial remedies with two (or more) drugs at a fixed dose may provide patients with better treatment options. Based upon understanding the various molecular regulation of pathological processes and principles of drug action, clinicians and pharmacologists are able to design new FDC to achieve optimum efficiency in clinical practice. In this sense the significance of FDC is no less than NME, because it is closer to clinical practice and directly meets the needs of patients. This article briefly analyzes the development of FDC from the microscopic characteristics of pathology and the molecular mechanism of drug action with influential examples.