Highlights ► Fluorinated reactive monomer (FAM) was successfully synthesized based on diisocyanate. ► Fluorinated cationic guar gum (FCGG) was prepared via modifying cationic guar gum with FAM. ► FCGG solution had unique associating and rheological behaviors. ► The relaxation time of FCGG solution increased significantly compared with cationic guar gum. ► FCGG solution possessed much better heat resistance.