In order to study the influencing factors on the breaking and recycling of guar gum fracturing fluid，the influence mechanism of residual thickener and crosslinking agent on the performance of fracturing fluid prepared by flow-back fluid was studied，from the aspects of performance change，existence state and content of residual thickener and crosslinking agent in flow-back fluid. The results showed that with the increase of breaking time or dosage of breaking agent，the viscosity of guar gum fracturing fluid and the extraction time decreased，and the proportion of small molecules increased. The enzymatic breaking was selective，and the ratio of mannose to galactose remained unchanged after enzymatic breaking. The oxidative breaking was not selective. With the extension of breaking time，the content of galactose decreased，and the molecular structure changed. Galactose side chain limited the helical formation ability of mannose main chain，which led to the decrease of water solubility and the formation of flocculent precipitate. The influence of residual thickener content on the swelling of guar gum was small，but the entangling and crosslinking between long-chain guar gum molecules were affected because of the small molecule crosslinking between long-chain guar gum molecules，which led to the decrease of shear resistance of fracturing fluid. The proportion of small molecules increased in multiple cycles of breaking solution，and the viscosity of breaking solution was greater than that requirement of flow-back solution. The sugar content of residual thickener should be controlled below 0.2% when the flow-back solution was recycled.