Forest biomass is important information for the forest management and the studies of global changes. Researches showed that SAR data is superior in the estimation of forest biomass. However the backscattering coefficients are not the direct measurements of forest biomass. It can be affected by forest canopy spatial structures. In this study, eight scenes of PALSAR data acquired from July 10^th 2007 to July 12^th 2008 were collected. The annual behavior of backscattering coefficients and coherence derived from these interferometric PALSAR data were investigated. The results showed that the summer data showed high backscattering while the winter data showed low backscattering. The coherence of PALSAR InSAR data was the highest in the summer lowest in the winter. The coherence from summer data was negatively correlated with forest biomass. But the coherence from spring data showed higher coherence in the areas with higher forest biomass. The difference between SRTM elevation and digital elevation model generated by PALSAR interferometric data in the summer shows the potential for forest biomass mapping.