The interlayer vertical transition structure is usually utilized to realize the miniaturization and high-density design of module structure, and plays an indispensable role in millimeter wave circuit wiring. In this paper, a vertical transition structure from microstrip to stripline is studied, which can be used in Q-band. A "water droplet" matching structure is adopted at the end of microstrip line, and the vertical transmission of Radio Frequency(RF) signals is carried out in the form of metal through holes connecting transmission lines. The three-dimensional High-Frequency electromagnetic Simulation Software(HFSS) is employed to establish the structure and compare the performance with that of other similar structures. The optimization results show that the reflection coefficient of this structure is less than -20 dB and the in-band insertion loss is better than 0.3 dB in 42~47 GHz, which can meet the requirements of engineering application. Compared with other vertical transition structures of the same type, it reduces the occupied area and maintains good transmission performance.