This paper explores a method to separate P- and S-waves from multi-component seismic data utilizing wave vector rotation in an affine coordinate system. We use a vector composition method within a sliding time window to derive non-orthogonal P- and S-wave vector directions. Then all wave vectors within the sliding window are decomposed into the parallel and orthogonal parts in the direction of the P- or S-wave vector, in order to recover true amplitude P- and S-waves. The parallel part is reserved as the true amplitude signal, while the orthogonal part is eliminated as the residual noise. We examine the behaviour of the method when applied to synthetic data with different signal-to-noise ratios. The method is also demonstrated to be effective on field seismic records.