This paper attempts to investigate the fracture toughness of the cracked concrete repaired by polymethyl methacrylate (PMMA) - a thermo-plastic polymer resin. A single-edged notch beam in three-point bending test was conducted to examine the performance of cracked concrete beam after reparation. Three concrete crack widths of 1 mm, 5 mm, 10 mm were designated to be repaired and examed. The fracture properties include critical stress intensity factor KIC by Jenq and Shah and fracture energy GF by Hillerburg, were evaluated for the concrete before cracking and after reparation. Four sand contents of 0%, 10%, 20% and 40% by volume were used in the PMMA mortars. From the testing results, it appears that the load capacity and fracture toughness of repaired concrete increased with the increasing sand content. And, the PMMA mortar made repaired concrete better strength and fracture toughness as well.