The main purpose of this study is to investigate the influence of fines content on static and cyclic behaviors of silty sands with different particle gradations. Three types of soil particle gradations, which are classified as A, B and C, were performed in sample sands from the Cian-Jhen riverside in Kaohsiung. Meantime the fines requested are added to the testing sand passing through an ASTM No.200 sieve. The relative densities of the specimens were set by preparation at 30%, 50% and 70% respectively with different fines contents of 0%, 5%, 15% and 25%. The results showed that fine soil particles have a remarkable effect on the decrease of internal friction angles and liquefaction resistance, and the relative densities of the specimens also have significantly positive effects on liquefaction resistance. The paper utilized also the concept of intergranular void ratio to investigate the correlation between the influence of fines on liquefaction resistance for silty sands and feasible roles of fine particles within the soils.