Abstract: Based on four surveys carried out during 2016 and 2017, weanalyzed the distribution and variation of resources of Sargassum thunbergii with random sampling method in three regions of Dalian, Qingdao and Wenzhou, China.The results showed that the morphology and biochemical composition of Sargassum thunbergii had obvious regional differences and time variations.The number of size distribution of Dalian was much more than Qingdao and Wenzhou.In October, the biomass of Qingdao(429 g/m²)was the largest in three regions.The biomass of Dalian in October, February and May were 931.3 g/m², 1453.1 g/m² and 2047.7 g/m², respectively. And, the number of primary branches of Qingdao were the largest in October, February and May, which were 4572/m², 5707/m², 3659/m².But, it appeared the lowest number(2199/m²) in July.Lateral branches were first found in Dalian, and the percentages of lateral branches withing lateral branches in three regions were highest in July.The number of lateral branches in Dalian was the highest (123±63/plant) and the longest (13.1 cm).The contents of Chlorophyll were higher in Dalian than others.However, the contents of phlorotannin of Qingdao and Wenzhou were higher than Dalian.The highest contents of phlorotannins appeared in May in Dalian and Wenzhou while it appeared in July in Qingdao.The results of our investigation showed that the population structure and morphological characteristics of Sargassum thunbergii were significantly different between regions and times, which may depended on anthropogenic and environmental factors.