Phase equilibria in Al-Ni-Sc ternary system have been measured through alloy sampling. According to the results from electron probe microanalysis and X-ray diffraction techniques, isothermal sections of Al-Ni-Sc ternary system at 1173 K and 1273 K were constructed, where four new ternary phases, tau 7 (Ni2Al5Sc), tau 8 (Ni2Al4Sc), tau 9 (NiAl2Sc3) and tau 10 (NiAlSc5), were detected along with the formerly reported ternary compounds, tau 1 (NiAlSc), tau 2 (Ni2AlSc) and tau 5 (NiAl2Sc). The existence of tau 3 (Ni7Al16Sc6), tau 4 (NiAl4Sc) and tau 6 (Ni3Al9Sc) reported previously in the literature was not confirmed in this work. And tau 1 shows large composition range at 1173 K and 1273 K.