Nano-gap and nano-tip have been widely exploited for attaining regions of "hot-spot" fields and high SERS(Surface Enhance Raman Scattering)-active substrates recently.[1-2] However,the simple and effective approach for the preparation of highly uniform and macroscopic SERS-active substrate is still a big challenge to the research community.Herein,we proposed a proof of concept SERS film based on agarose hydrogel and gold nanorods(Au NRs)hybrid materials.Gold nanorods were pre-dispersed in agarose hydrogel,which is a three-dimensional matrix formed with plenty of channels and pores that molecules can pass.After cast and dried,the agarose hydrogel lost most of water and flattened into an ultrathin film.With the film thickness decreasing,the distance between Au NRs become shorter in vertical direction to generate a large amount of "hot-spot" for signal enhancement.It should be noted that Au NRs are dispersed in agarose solution before the formation of hydrogel,and during the drying process,the agarose hydrogel acts as a trapping-matrix to prevent the aggregation of Au NRs.Therefore,the distribution of Au NRs in the final ultrathin film is highly uniform.We demonstrate the SERS activity and uniformity of this agarose/Au NR film could be controlled by varying the concentration of agarose and Au NRs.Besides,the flexibility,thickness and sensitivity of SERS film material exhibits great potential for SERS analysis.