For the classical Lotka—Volterra predator-prey system, new notion I-optimal curve ξ_I is introduced. This curve is disposed in the phase space of the system. The curve ξ_I intersects each trajectory γ_c of Lotka—Volterra system at least once. The points of ξ_I possess the following optimal property: if (m, M) ξ_I ∩ γ_c0, then after a “jump” with magnitude I to the origin of coordinates, it hits a trajectory γ_c1 and c₁ is minimal; i.e., γ_c1 is the “nearest” to the stable centre. The minimality concerns the rest points of initial trajectory γ_c0, from which the “impulsive jumps” (subtractings) with magnitude I to (0,0) are realized. The monotonicity, continuity, and linear asymptotical behaviour of ξ_I curve are proved.