To explore the influence mechanisms on traffic congestions problems in expressway interchange diversion area, this study analyzed the relationship between the abnormal lane-changing rate-flow and speed-abnormal lane change rate curves under different diversion ratios and heavy vehicle mixing rates and revealed the influence of traffic volume characteristics parameters on the abnormal lane-changing behavior in the diversion zone and the abnormal lane-changing behavior on the travel speed under specific conditions. The results showed that with the increase in traffic volume, the abnormal lane-changing first decreased and then increased, and the increase of diversion ratio and heavy vehicle mixing rate would increase the abnormal lane-changing behavior of drivers. When the traffic volume was greater than 3600 pcu/h, with the increase of diversion ratio or heavy vehicle mixing rate, the influence of abnormal lane-changing rate on the average speed of vehicles in the diversion area increased, especially with the diversion ratio greater than 40% or heavy vehicle mixing rate greater than 10%. These findings can provide theoretical basis for alleviating traffic congestion and regulating driver behavior, which have a positive impact on improving traffic efficiency and safety in diversion areas.