Abstract: This paper studied the accessibility level and its spatial pattern evolution along Circum-Bohai-Sea high-speed rail. The paper first evaluated the urban accessibility dynamic changes with and without Circum-Bohai-Sea high-speed rail(HSR) by two accessibility indicators, i.e. the weighted average time, and the economic potential. Then the spatial differentiation of the accessibility dynamic changes with and without Circum-Bohai-Sea HSR was performed respectively by using ArcGIS. Finally, the spatial differentiation of the accessibility dynamic changes was used to reveal the evolution and reshaping of spatial patterns in the Circum-Bohai-Sea areas. The results are as following. First, the opening of Circum-Bohai-Sea HSR has greatly improved the accessibility level along Circum-Bohai-Sea areas. And the weighted average travel time of the nodes along Circum-Bohai-Sea HSR decreases by about 59%. The economic potential of the nodes along Circum-Bohai-Sea HSR increases by around 178%. Second, before and after opening the Circum-Bohai-Sea HSR, the accessibility level of various urban agglomerations in the Circum-Bohai-Sea areas is different. The accessibility level of Beijing-Tianjin-Hebei urban agglomeration is stronger than that of the Shandong Peninsula urban agglomeration and Central Southern Liaoning urban agglomeration. However, the accessibility improvement degree of the Beijing-Tianjin-Hebei urban agglomeration and the Central Southern Liaoning urban agglomeration is weaker than that of the Shandong Peninsula urban agglomeration. Third, spatially, the accessibility optimal element shows a decreasing trend from Circum-Bohai-Sea HSR axis to the periphery areas. And the accessibility level and the accessibility improvement degree of the nodes, which are located at the beginning and end of the Circum-Bohai-Sea HSR line is weaker than those nodes, located in the middle of the HSR line. Finally, affected by the Circum-Bohai-Sea HSR, the gradual evolution and reshaping of regional spatial pattern become more and more complicated. The spatial polarization phenomenon of Circum-Bohai-Sea HSR shaft will further enhance. The integration process of the Beijing-Tianjin-Hebei, Shandong Peninsula and Central Southern Liaoning urban agglomerations will appear, resulting in a combination effect of 1+1+1>3. Circum-Bohai-Sea port agglomerations connect the different rails, and the spatial differentiation and combination are becoming more and more complex. Circum-Bohai-Sea HSR will be integrated with “the economic corridor of China, Mongolia and Russia” under the background of “the Belt and Road” initiative.