Based on the density functional theory, the structural, lattice dynamic stability and electronic properties of chalcopyrite AgAlSe2 under different pressures were investigated by generalized gradient approximation.The result show that, the lattice parameter of the chalcopyrite AgAlSe2 is consistent with the experimental values at 0 GPa, and the mass density, Se-Ag， Se-Al bond length and lattice constant a have a sudden increase, the relative cell volume V/V0 and lattice constant c suddenly decrease, and the phonon spectrum presents imaginary frequency, the structure becomes unstable, and the band gap changes abruptly, and the value shows a decreasing trend near 13.9 GPa. These results indicate that the chalcopyrite AgAlSe2 undergoes a structural phase transition near 13.9 GPa. This research provides information support for AgAlSe2 crystals under theoretically high pressure.