The static creep mechanism and behaviour of Al-Zn-Mg alloy have been investigated under condition of constant stress tension creep test in the temperature and stress range of $170-260^{circ}C$ and 5-12.5 $kg/mm^2$ respectively. The experimental result are follows : The stress exponent value for creep was observed to about 7.3-6.43 and the activation energy for creep deformation was 44-41 kcal/mol. Larson-Miller parameter P for the crept specimens under the creep condition was obtained as P = (T + 460) (log $t_r$ + 8.6). Emperical equation for the creep rate was obtained by the computer simulation as follows. $${varepsilon};=;exp[(-5.519{ imes}10^{-4}{sigma}+2.33{ imes}10^{-2})T-6.98{sigma}+18.295]{ imes}{sigma}^{-0.0142+10.18}exp[frac{(-6{sigma}+47.8)1000}{RT}]$$ Fracture was dominated by intergranular mechanism over the experimental range.