In order to increase the viscosity of guar gum fracturing fluid formulated by oilfield produced water，the produced water was pretreated by self-made polysilicate flocculant and then modified by chelating agent OM-002，iodine-containing stabilizer P-104 and heavy-metal zirconium compound HZR-02. The influence of OM-002，P-104 and HZR-02 on the viscosity of guar gum fracturing fluid formulated by the modified water was investigated. The study results showed that the dynamic viscosity of fracturing fluid formulated by pretreated produced water decreased significantly in comparison to fresh water，while that increased by modifying oilfield produced water. The produced water modified by three additives（OM-002、P-104 and HZR-02）at the same time had more significant thickening effect than single additive. On the condition of 65℃ and a combination of OM-002，P-104 and HZR-02 in mass ratio 10∶2∶5，the dynamic viscosity of fracturing fluid increased from 74 mPa·s to 306 mPa·s after the fluid formulated by modified produced water，and the temperature and shearing resistance of fracturing fluid were augmented.