Engineered ultrafine porous Fe2SiO4/C composites (FS221/C, FS263/C and FS325/C) are successfully fabricated by solid state reactions from the mixture of ammonium citrate, ferrous oxalate dehydrate and nano porous SiO2 with different specific surface area (221, 263 and 325 m(2) g(-1)). XRD results proved that alpha-Fe2SiO4 phase are formed in the three samples. SEM and TEM results indicate that all the three samples are ultrafine composites and the particle size of FS325/C is the smallest. Pore structure analysis indicates that the external surface area of the ultrafine porous Fe2SiO4/C composites can be well controlled by tuning the surface area of nano porous SiO2 and the external surface area of FS325/C is the largest among the three samples. These unique features make FS325/C possess the highest reversible lithium storage capacity, best rate performance, longest cycling life, lowest charge transfer resistance and highest lithium ion diffusion coefficient among the three samples.