A specific issue in seismic analysis of large span bridge, study on inconsistent ground motion input is reviewed in this paper. The building of spatial model for ground motion field based on observation of motions on dense arrays and coherence validation of the synthesized ground motion field are deal with respectively. Points are emphasized that spatial correlation between motions with distance of several hundred meters to each other comes from one same source and very similar path, similar/different site condition. A comprehensive procedure taking source, path and site condition all into account to synthesize the motion field is convenient to reveal and express the physical nature of the motion field. Spatial structure of a synthesized motion field is validated by means of the coherency coefficients. The result is consistent with the conclusion from the statistics of the observed data on some dense arrays.