[en] An investigation into the high-pressure behavior of AX₂-type iron pnictides was conducted using first-principles calculations based on density functional theory within the generalized gradient approximation. Our results demonstrate that a phase transition from the marcasite to the CuAl₂ occurs at 108 GPa for FeP₂, at 92 GPa for FeAs₂, and at 38 GPa for FeSb₂, accompanying a semiconductor-to-metal crossover. A linear relationship between bulk moduli and the inverse specific volume is proposed to be B₀ = 17 498/V₀-45.9 GPa for the marcasite-type phase and B₀ = 31 798/V₀-67.5 GPa for the CuAl₂-type phase. According to the observed structural evolutions, we claim that the regular marcasite transforms to the CuAl₂-type phase and the anomalous marcasite transforms to the pyrite-type phase at high pressures.