Investigations of standing stock of phytoplankton (chlorophyll a) and primary productivity were carried out in the Bering Sea along a longitudinal (the BR line, 51°38′～60°40′N, 168°06′E～178°15′W) and a latitudinal (the BS line, 64°20′N, 171°30′W～167°00′W) transects during the 2nd Chinese National Arctic Research Expedition in the summer of 2003. The stations of the BR line were surveyed on 24～27 July (early summer) and the survey of the BS line took place on 28～29 July (early summer) and on 12～13 September (latter summer), respectively. The results showed that the surface chlorophyll a concentrations were 0.199～1.170 μg/dm^３, and the average value was （0.723±0.283) μg/dm３ on the BR line. For the BS line, surface chlorophyll a concentrations were 0.519～4.644 μg/dm^３ (average (1.605±1.194) μg/dm^３) and 0.568～14.968 μg/dm３ (average (5.311±5.656) μg/dm３) during the early and latter summer, respectively. The average value in the latter summer was much higher than that in the early summer. The high values (more than 4.0 μg/dm３) occurred at stations of the BS line in the southern Bering Channel. Chlorophyll a concentrations in the sub-surface layer were higher than in the surface layer.The potential primary productivities varied between 0.471 and 1.147 mgC/(m³•h) on the BR line, with average rates of （0.728±0.315) mgC/(m^３•h). The potential primary productivities on the BS line were much higher than that of the BR line, ranging from 1.227 mgC/(m^３•h) at early summer to 19.046 mgC/(m^３•h) at latter summer. The assimilation number of photosynthesis was 0.45～2.80 mgC/(mgChla•h).