This paper first develops a synthetic urban power grid model with solar photovoltaic (PV) and electric vehicles (EV) using public data from utilities, regulators, open-source datasets, and relevant publications. Then, a probabilistic security assessment approach is proposed to evaluate the impact of the PV and EV integration under different penetration and uniformity levels, deployment scenarios, and uncertain daily curves. The security indexes, including maximum and violation rates, quantify the bus voltage magnitude and branch power flow. Simulation results show that the integration of PV and EV can substantially affect the voltage and branch power flow, which may cause security risks to distribution networks. Moreover, integrating PV and EV reshapes the netload daily profiles and may generate the reverse active power in substations and branches. Although the power grid model is synthetic, the modeling process and security assessment method can be a reference for similar studies of realistic distribution grid systems.