For filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) and singular value decomposition (SVD)-based beamforming, the beamformers may experience significant changes between adjacent subchannels, therefore destroy the orthogonality among FBMC/OQAM realvalued symbols, even under channels with moderate frequency selectivity. In this paper, we address this problem by propose a smoothing criterion and method under the structure of frequency spreading FBMC (FS-FBMC), namely phase factor optimization, to smooth the beamformers from tone to tone (FS-FBMC tones). Simulations are conducted under the scenario of IEEE 802.11n wireless LAN. Results show that the proposed smoothing method greatly improves the smoothness of beamformers, therefore effectively suppress the leaked ICI/ISI.