Abstract: Range-dependence of airborne bistatic clutter degrades space-time adaptive processing STAP performance in clutter suppression, and spectrum registration-based nonuniform frequency sampling (RB-NFS) method can mitigate range-dependence in clutter data domain. Problems confronted by RB-NFS in airborne bistatic radar are analyzed and modified. For insufficient clutter suppression and the complexity of constructing clutter space-time steering matrix, two approaches,using generalized inverse matrix and adoption of diagonal loading technique, are proposed; and for estimation precision of clutter covariance matrix in RB-NFS, obtained by maximum likelihood principle, is affected by the number of training samples, one new method to compute the matrix is presented. Simulations testify the validity of analysis and efficiency of the methods proposed. The STAP processor with modified RB-NFS achieves approximately optimal capability using only two training samples.