In the early summer of 2016, we investigated the primary productivity (PP) and productivity index (I) using the stable isotope ¹³C tracer method, and other environmental parameters, including chlorophyll-a (Chl a), temperature (T), salinity (S), and Secchi depths, in order to examine the relationships between PP distribution characteristics and environmental parameters in Bohai Bay. The results show that there were three obvious water masses with different temperature and salinity characteristics in our study area, because of the river discharge and cold water mass at the mouth of the bay. Chl a concentrations ranged from 1.27 to 20.82 mg/m³, and declined from the surface to the bottom and from the nearshore to offshore. In the coastal high-T and low-S zone, nutrients from river runoff and relatively higher temperature supported phytoplankton growth and thus Chl a was found as high as (8.37±2.90) mg/m³ on average, and 27.5% of the samples with Chl a concentrations higher than 10 mg/m³ were from the surface layer, probably suggesting the possibility of an algal bloom when the temperature increases as summer progresses. Comparatively, Chl a concentrations in the central area and mouth of the bay were much lower than those in the coastal zone, probably because of phosphate and temperature limitations. The PP was estimated to be from 44.79 to 792.73 mg C m^-3 d^-1, with a mean value of (144.13±137.79) mg C m^-3 d^-1. Controlled by high phytoplankton biomass and sufficient nutrients, PP also exhibited a declining trend from the coast towards the offshore. Productivity index was estimated to be from 0.79 to 5.90 mg C/(mg Chl a·h) with a mean value of (3.40±1.33) mg C/(mg Chl a·h). Depth-integrated primary productivity (∑PP) of the water column was also estimated and it ranged from 56.88 to 772.31 mg C m^-2 d^-1, with a mean value of (232.26±126.47) mg C m^-2 d^-1. It was found that ∑PP, controlled by Chl a in the coastal zone, showed high-value stations off the Haihe River and Huanghua Drainage River Estuary. Further, in the central area and the mouth of the bay, affected by the transparency (the euphotic layer was deeper), ∑PP showed several high-value stations.