Silica particles were used as a filler to produce silica-epoxy composite. Silica particles with two mean diameters of 1 mu m and 37 mu m and filler content of 20. 30, 40. and 60 wt.% were used to investigate the effect of particle size and filler content on the fracture behavior of epoxy resin composite, respectively. The fractural behavior of composites was characterized by linear elastic fracture mechanics according to standard of ASTM-D5045 in which three-point bending test procedure was used to investigate plane-strain fracture toughness (K-1C) and strain energy release rate (G(1C)) of the composite specimens. Glass transient temperatures of the samples were evaluated by using differential scanning calorimetry (DSC). Fracture surfaces of the produced specimens were examined by SEM. Tbe highest Young's modulus value was 10.48 GPa for the sample produced with 37 gm particle size and 60 wt.% filler content and it was found that a considerable increase was obtained according to the 3.05 MPa values of the unfilled epoxy. Experimental results show that fracture toughness value of the silica filled epoxy composite was improved by 98% compared to unfilled epoxy.