Using an isospin- and momentum-dependent modified Gogny (MDI) interaction, the Skyrme-Hartree-Fock (SHF) approach, and a phenomenological modified Skyrme-like (MSL) model, we have studied the incompressibility K sat (δ) of isospin asymmetric nuclear matter at its saturation density. Our results show that in the expansion of K sat (δ) in powers of isospin asymmetry δ, i.e., K sat (δ) = K0 + K sat ,2δ2 + K sat ,4δ4 + O(δ6), the magnitude of the 4th-order K sat ,4 parameter is generally small. The 2nd-order K sat ,2 parameter thus essentially characterizes the isospin dependence of the incompressibility of asymmetric nuclear matter at saturation density. Furthermore, the K sat ,2 can be expressed as [Formula: see text] in terms of the slope parameter L and the curvature parameter K sym of the symmetry energy and the third-order derivative parameter J0 of the energy of symmetric nuclear matter at saturation density, and we find the higher order J0 contribution to K sat ,2 generally cannot be neglected. Also, we have found a linear correlation between K sym and L as well as between J0/K0 and K0. Using these correlations together with the empirical constraints on K0 and L, the nuclear symmetry energy E sym (ρ0) at normal nuclear density, and the nucleon effective mass, we have obtained an estimated value of K sat ,2 = -370 ± 120 MeV for the 2nd-order parameter in the isospin asymmetry expansion of the incompressibility of asymmetric nuclear matter at its saturation density.