Soft open point (SOP) is an emerging regulation device with effective and flexible real-time control capabilities in active distribution network (ADN). For managing active and reactive power flow, SOP has a wide range of application prospects nowadays. In this paper, an improved control method with adaptive dynamic reference (ADR) control is proposed for a SOP in medium-voltage ADN. The modeling and design of the ADR controller is studied to guarantee smooth and stable operation of SOP during step-change of power reference. The DC voltage fluctuations caused by step-change of power is greatly reduced using the proposed control strategy. The validities of the proposed control strategy are verified by simulation model of IEEE 33 Bus ADN with SOP using RTDS/RSCAD.