The firing density is an important parameter to evaluate the firing effect of rapid-fire weapons, and the multi-sky-screen target testing system is widely used in the measurement of firing density of rapid-fire weapons. However, due to the influences such as the transportation, repeated installation and movement of multi-sky-screen target, the change of ambient temperature in outfield testing, and the long-time usage, the measurement error of the firing density becomes larger. For the calibration of firing density of multi-sky-screen target, a method based on double theodolites and high-accuracy bullet holes screen was proposed. The coordinates of the bullet holes in the bullet holes screen were measured by intersection measurement of double theodolites, and then the density parameters were calculated by the density formula. The calculated density parameters were compared with that of the multi-sky-screen target to complete the calibration. By the firing practice, the uncertainty of firing density measured by double theodolites combined with bullet holes screen was evaluated. The results show that the uncertainty of the firing density measured by the proposed method is 1.6 mm, which can be used for the calibration of the multi-sky-screen target density.