Abstract: There is the Triangle Size Effect （TSE） in wind measurements with Spaced Antenna （SA） method due to electronic noise and ground clutters etc. Another possible cause （non-stationary of atmosphere） of TSE and the mechanism of its effect to wind measurements was discussed in this paper. The work also presents Increment＇s Cumulant Approach （ICA） to eliminate the nontationary of atmosphere and ground clutter based on the analysis of the causes of TSE; the analytical expression of one dimension mean velocity can also be obtained by the special case of Increment＇s Cumulant Approach （the 2nd order zero-lags ICA）. In addition the high order （k ≥ 3） cumulant of increment are proposed to suppress Gaussian noise. The comparisons between FCA and ICA with non-stationary and ground clutter by numerical simulations show that the measurement errors of ICA are much less than those of FCA by comparing mean horizontal velocities （output of simulations） and input velocities of mode.