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 325m2 g−1). XRD results proved that α-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.