The core of diagnosing and treating diseases in traditional Chinese medicine lies in syndrome differentiation. The eight principles of syndrome differentiation serve as guidance for syndrome differentiation. As one of the eight principles of syndrome differentiation， the differentiation of deficiency and excess is the basic and critical method. Ischemic stroke is currently the leading cause harming the health of Chinese residents. Although the hypotheses about the cause of ischemic stroke have evolved from external wind to the later internal wind and to the modern theory of toxin damaging the brain collaterals， they all believe that this disease is rooted in internal deficiency and external excess. According to available studies， although stroke is characterized by complex pathogenesis and rapid progression of syndromes， the key cause evolution has a regularity， that is， from excess to deficiency. This article analyzes the historical evolution of the etiology， pathogenesis， and syndrome differentiation schemes of stroke. There are diverse schemes for the syndrome differentiation of stroke， which make it difficult to choose in clinical practice. In view of this problem， this paper puts forward a new approach of staging sequential treatment of ischemic stroke based on the differentiation of deficiency and excess according to the evolution law of the key cause of stroke. Furthermore， we conducted a randomized controlled study on 100 patients with ischemic stroke to evaluate this new approach. The results showed that the staging sequential treatment of ischemic stroke based on the differentiation of deficiency and excess demonstrated definite clinical efficacy. In addition， this article reviews the previous research results of our team and the research achievements of other teams to preliminarily explore the relationship between stroke syndromes and biomarkers， aiming to provide an objective basis for unveiling the pathogenesis of stroke. In summary， according to the key cause evolution （from excess to deficiency）， the treatment of ischemic stroke by stages based on differentiation of deficiency and excess can facilitate the rapid intervention and improve the clinical efficacy on ischemic stroke.