Driver’s risk perception ability is of great significance to traffic safety. Driver’s risk perception ability is reflected in the risk handling in traffic situation and has a great impact on driving decisions, especially speed decisions. However, the mechanism of the influence of risk perception on driving decisions under risk situations is still unclear. According to standardized risk perception test, we divided drivers into high risk perception ability (H-RPA) group and low risk perception ability (L-RPA) group. Participants were shown traffic pictures with different levels of risk and asked to make decisions about whether to slow down, while their electrical brain responses were recorded. All participants were interviewed after the experiment. The results showed that in the low-risk traffic situation, compared to the drivers with H-RPA, the drivers with L-RPA made less deceleration decisions and evoked larger N1 and smaller P1 amplitude. 93.75% of the drivers with L-RPA stated in interviews that they did not notice the traffic risks on the road. The results show that risk perception affects the allocation of attention to risks in traffic situations, leading to a decrease in the safety of driving decisions. Our research results provide a reference for the training of safe driving skills for drivers.