Compared　with　natural　aggregate,recycled　aggregate　has　lower　apparent　density,higher　water　absorption　and　larger　crushing　index.　Therefore,there　are　some　defects　in　the　performance　of　recycled　aggregate　concrete　(RAC).　In　this　paper,nano-SiO2　solution　was　used　to　strengthen　RAC.　Three-point　bending　beam　method　was　adopted　to　conduct　fracture　experiment　of　specimens　with　varying　recycled　aggregate　replacement　rates　(0,　50%,　70%,　100%)　and　specimens　with　varying　replacement　rates　(50%　and　100%)　and　varying　SiO2　addition,12　groups　of　60　specimens　in　all.　Double-K　fracture　parameters　were　used　to　assess　the　fracture　property　of　recycled　concrete　and　to　investigate　the　effect　of　recycled　aggregate　replacement　rates　and　addition　of　SiO2　on　the　fracture　property　of　recycled　concrete.　The　results　show　that　the　initial　cracking　toughness　and　the　unstable　fracture　toughness　of　RAC　decreased　with　the　increase　of　RAC　rate.　Appropriate　amount　of　nano-SiO2　can　improve　the　fracture　toughness　of　RAC,when　the　replacement　rates　of　recycled　aggregate　were　50%　and　100%　respectively,and　the　content　of　nano-SiO2　was　1.0%,the　enhancement　for　initial　cracking　toughness　and　unstable　fracture　toughness　of　recycled　concrete　was　the　highest,reaching　0.6929　MPa•m1/2　and　1.3073　MPa•m1/2　respectively　for　recycled　concrete　with　50%　recycled　aggregate　and　0.5552MPa•m1/2　and　1.2410MPa•m1/2　respectively　for　recycled　concrete　with　100%　recycled　aggregate.　©　2018,　China　Water　Power　Press.　All　right　reserved.