The cutting frequency of the vertical cutter in the traditional rape combined harvester at different speeds keeps constant. It will cause the large re-cutting or leakage zone and lead to the increase of cutting header loss. At the same time, the work performance will be unstable. A double vertical cutter follow-up control device driven by two stepper motors was designed. And the influence of different advancing speeds on the cutting area and the cut off area of vertical cutting was analyzed. Considering the influence of rapeseed maturity and other factors, the best theoretical matching relationship between advancing speed and cutting frequency for vertical cutter was obtained. Then, the servo control system was designed for cutting frequency of vertical cutter based on S7-1200PLC. By detecting the forward speed signal of the machine and controlling the stepper motor according to the best theoretical matching relation, the follow-up control for vertical cutter frequency was realized. The comparison test of the harvested rapeseed after one week of applying the dehydrating agent showed that the total loss rate of the rapeseed header using the vertical cutter frequency follow-up control system was decreased by 36.15%~41.16%, and the loss rate of the vertical cutting knife was decreased by 40.84%~48.20%. When the characteristics of rapeseed and the harvesting conditions of the machine were changed, the magnitude of total loss rate of header and the loss rate of vertical cutter may be changed, but the downward trend was consistent, and more working conditions were needed for comparative analysis.