The currently used formulas for calculating the trajectory of bow-spray for the TSHD are based on the projectile theory, but they do not consider the mixing and expending effects due to jet characteristics. Therefore, they cannot be used for calculating the interface between slurry falling and the land/water surface. On the basis of the spray distance calculation model accounting for air resistance, in this study, a new method was established for calculating the trajectory and extension range of bow-spray by introducing the basic characteristics of jet flow. First, the practicability and accuracy of the new model were calibrated and validated by field tests, numerical simulations, and the air resistance-based calculation model of the spray distance. Then, the effects of the jet propagation coefficient, the injection angle, and the nozzle diameter on the bow-spray distance and falling boundary were analyzed and are discussed. The results indicate that by decreasing the jet propagation coefficient through the optimization of the jet nozzle structure, it is possible to extend the optional operating position and reduce sediment loss. For the injection angle of 40–45°, the maximum spray distance and furthest inner boundary can be reached. However, for the injection angle of 30–35°, the falling angle is smaller, which is conducive to sediment loss control. There can be certain effects on the spray distance and falling boundary of the nozzle diameter. Therefore, determining an appropriate injection angle and a nozzle diameter based on specific operation conditions and further analyses is important.