Abstract: To address the over-reliance on empirical selection of the window width for zero-Doppler clutter (ZDC) filtering in turntable radar cross section measurements, a window-width range determination method based on background residual suppression and target scattering preservation constraints is proposed. First, an angular-domain frequency response model of rectangular sliding-window ZDC filtering is established to analyze the relationship between the window width and both the suppression range of near-zero angular-domain frequencies and the preservation of the target’s low-angular-domain-frequency components. Then, the background residual is constructed using two background measurements, and the ratio of the residual power after filtering to that before filtering is used to determine the upper bound on the window width under the background residual suppression constraint. Meanwhile, target simulation data are used to calculate the average radar cross section attenuation within a specified angular sector, thereby determining the lower bound on the window width from the target scattering preservation constraint. Simulation results for an ideal two-point target and a 60° dihedral target show that the proposed method can identify a candidate window-width range satisfying both constraints, and a representative window width within this range can suppress near-zero angular-domain-frequency background residuals while improving consistency with the pure-target result. Parameter analyses show that the background residual level and the required background margin mainly affect the upper bound of the candidate range, whereas the allowable attenuation threshold for the target’s average RCS mainly affects the lower bound. Compact-range measurements of a two-sphere target show that, after the extended-range-gate data are processed using a representative window width selected from the candidate range, the resulting RCS curve becomes more consistent with the target-range-gate reference result, achieving a reasonable trade-off between background residual suppression and target scattering preservation. These results indicate that the proposed method can provide an interpretable quantitative basis for selecting the ZDC filtering window width in turntable RCS measurements.