The coherent excitation of optical device through the interference effect of multiple beam provides a practical way to enhance the degree of real-time control of the optical response of device. In this work, the coherent control of polarization transformation of Bloch surface wave supported by dielectric multilayer is studied. The grooves are introduced into the top layer of the dielectric multilayer to achieve the polarization transformations of Bloch surface wave. Two coherent beams of Bloch surface waves are incident on the grooves from the left side and the right side of the structure, respectively. The polarization transformation efficiency of Bloch surface wave can be controlled in real time by designing the phase difference of polarization transformation coefficients and the phase delay of the incident coherent beams. Moreover, the output ports of polarization transformation of Bloch surface waves can be selectively excited. By using the proposed method, the controllable port transmission of Bloch surface wave related polarization component can be achieved. In this work, the design of phase difference from the polarization transformation coefficients is achieved by changing the separation distance of grooves. The predicted polarization transformation phenomena under the excitation of coherent beams are evidenced by the rigorous electromagnetic simulation. The research results have potential applications in on-chip integration of photonic circuitry.