Temporal power spectra of low-order modes［tilt(Z-tilt, G-tilt), defocus, astigmatism, coma］ of atmospheric turbulent wavefront are deduced by introducing generalized phase spatial spectrum. Numerical results and analysis are given under the conditions of horizontal atmosphere, observation of star objects and monitoring of spatial objects. The results show in horizontal atmosphere, the temporal power spectra is proportional to the 4/3-6β/11 power (β is the power-law exponent of phase power spectrum) of the frequency v for tilts and v0 for defocus, astigmatism and coma for small v values respectively. For large v values, all the spectra have the same asymptotic behavior and decrease as v-β-2 except for G-tilt whose power spectra decrease as v-β in horizontal atmosphere. The temporal power spectra is influenced by outer scale of atmospheric turbulence and with the decrease of outer scale, the spectra becomes steeper and steeper.