Aiming at the shortcomings of the conventional sky screen that cannot be used in low natural light or at night, a lase sky screen with all-weather operation is investigated in this paper. The detection sensitivity of the laser sky screen is directly proportional to the voltage amplitude of the projectile signal, which ultimately determines its performance and the accuracy of velocity measurements. Drawing upon the mechanism of the laser sky screen and photometric theory, the main factors affecting the detection sensitivity are analyzed, the calculation formula of the reflected luminous power when a projectile passes through different positions within the detection light screen, and the changing rules of the signal amplitude of different positions within the detected light screen are simulated and analyzed. Through the shooting test with 7 mm steel balls, the distribution of the signal amplitudes at different locations within the screen aligns well with the predicted results. This research establishes a mathematical model for sensitivity in the context of laser sky screen applications in testing fields, providing a technical reference for ongoing performance enhancements.