Abstract: The difficulty of beyond visual range multi-target tracking is mainly determined by target density ρ and maneuverability a, while the capability of tracking system is limited by positioning error σ and revisit time ∆t. To deduce constraint relationships among four variables, the multi-target tracking process is modeled from the angles of signal and systems, mapping tracking capability limit to sampling limit of track signals. Then the relationship between sampling rate and four variables is derived. Taking the typical scenario as an example, the constraint relationship analysis of variables are analyzed. The method can be applied to design tracking systems and classify the difficulty level of the mission scenario.