Abstract: The equivalent deterministic input technique （EDIT） for multi-input-random process published recently by B. Etkin, P. Hughes and S. Zhu is first reviewed briefly in this paper. Then a formula of linear transformation （Eqs. 7,8） is derived and the singularity of the equivalent input function is shown（Eq. 9）. By analysing the characteristics of the turbulence spectral maxtrix （Eq. 11） for the longitudinal motion of an aircraft, including two gust velocities and one gust gradient, it turns out that only two （rather than three） equivalent input vectors are needed （Eq.15）.The Dryden's spectra of atmospheric turbulence in current use （Eq. 14） are decomposed into U11, U22, U33, and the inversed Fouriertransform is performed subsequently （Eq. 3） to obtain the equivalent deterministic input function u11, u22, u32 （ = uE32 + uO32） （Figs.1, 2） for the reference flight condition. These curves are then fitted by simple expressions （Eq. 16）. The method and procedure for numerical computation or simulation of the aircraft response to turbulence in the time domain are proposed and discussed（Eqs. 18, 20, 21）. A numerical example is given for comparing the results from EDIT and PST （power spectral technique） （Table 1）.