Sea breeze fronts are closely related to the severe convective weather that occurs in coastal regions. Changes in the underlying surface of the coastal region, caused by urbanization, influence the characteristics of the sea breeze front. We applied the WRF (Weather Research and Forecasting) model, coupled with a new generation urban physics scheme, the UCP-BEM (Urban Canopy Parameterization-Building Energy model), to study the effects of urban underlying surfaces on sea breeze front characteristics in the Bohai Bay region. The results showed that the low-level sea breeze was weakened noticeably because of the roughness of the urban underlying surface, leading to decreases in low-level convergence, upward motion, and the inland distance of the sea breeze front. The combination of larger upward sensible heat flux, smaller upward moisture flux, and weaker sea breeze, caused by the thermal and dynamic properties of the urban underlying surface, inhibited the cooling and moistening of the low-level atmosphere from the relatively cool and moist sea breeze. The frictional force effect of the urban underlying surface on sea breeze circulation resulted in the lifting of the sea breeze, expanding the vertical atmospheric cooling and moistening range. The available convective potential energy behind the sea breeze front decreased correspondingly, but its vertical distribution expanded, leading to the uplifting of the convective inhibition center. Moreover, the static instability zone thickened while the dynamic instability zone above it thinned, but the thickness of the whole instability zone remained constant.