Abstract: Under the background of ‘the Belt and Road’ and ‘China-Mongolia-Russia Economic Corridor’ initiatives, this paper studied the urban accessibility level, regional accessibility pattern and regional spatial effects along the Primorsky No.1 and No.2 transportation corridors. First, the evaluation of urban accessibility level with and without Primorsky No.1 and No. 2 high-speed rails (HSRs) opening was conducted with two indicators, i.e., the weighted average travel time, and the economic potential. After the evaluation, the spatial differentiation pattern of the accessibility changes with and without Primorsky No.1 and No.2 HSRs opening was performed respectively using ArcGIS. On these bases, the regional spatial effects brought by Primorsky No.1 and No.2 HSRs opening were studied. The results are as following. First, the urban accessibility level will be greatly improved by the opening of Primorsky No.1 and No.2 HSRs. All adjacent cities will be integrated into ‘1 h HSR communication circle’ and the whole journey will be integrated into ‘4 h HSR communication circle’ along Primorsky No.1 and No.2 corridors, respectively. The HSR accessibility of Primorsky No.1 corridor is stronger than that of Primorsky No.2 corridor. But the HSR accessibility improvement degree of Primorsky No.1 corridor is weaker than that of Primorsky No.2 corridor. Second, spatially, along Primorsky No.1 and No.2 corridors, the HSR accessibility level of the cities which are located in China is stronger than those cities located in Russia, showing the ‘High West, Low East’ patterns. The HSR accessibility improvement degree of the cities which are located in Russia and Sino-Russian border is stronger than those cities located in China, showing the ‘High East, Low West’ patterns. Third, Primorsky No.1 and No.2 corridors could connect the China’s ‘Heilongjiang Land Sea Silk Road Economic Belt’ and ‘Changchun–Jilin–Tumen Development Pilot Zone’ respectively, gradually involving into the development of China’s Harbin-Changchun Megalopolis. Relying on Harbin (China) and Changchun (China), Primorsky No.1 and No.2 HSRs could connect Northeast China–Beijing HSR, accelerating the diffusion of population, economy and other flows from China’s Beijing-Tianjin-Hebei Urban Agglomeration to Northeast China, and then to Russia’s Far East Federal District. Relying on Suifenhe (China) and Hunchun (China), Primorsky No.1 and No.2 HSRs could be conducive to the development of the second largest sea channels for Northeast China, creating the Northeast Asian Urban Belt, and new sea-rail intermodal pattern among China, Russia, Democratic People’s Republic of Korea, Japan and Republic of Korea. Relying on Vladivostok (Russia) and Zarubino (Russia), Primorsky No.1 and No.2 corridors could connect the ‘Ice Silk Road’, building the ‘Sino-Russian Northern Maritime Corridor’ and ‘Sino-Russian Arctic Blue Economic Areas’.