Simultaneous radiation grafting method (,60,Co γ-rays as the radiation source) was used to prepare xanthan gum-graft-N-vinypyrrolidone (XG-g-NVP), and the influence factors of the grafting degree was preliminarily studied. The structure of the grafted copolymer was characterized by the Fourier-transform infrared spectroscopy (FT-IR) and thermo gravimetric analysis (TGA), and the solution viscosity properties of the grafted copolymer in low grafting rate were studied by rheometer. The results show that the grafting rate increases with absorbed dose and gradually achieve to the balance. The grafting rate reaches maximum when the xanthan gum concentration is 10 g/L or the mass ratio is 10:1 meanwhile the other two factors are in a certain experimental value range. FT-IR figure shows that the grafting reaction occurs in NVP vinyl part and lactam structure is retained. Thermo-gravimetric analysis shows that XG-g-NVP enhanced thermal stability of xanthan gum. The properties of XG-g-NVP solution show that grafting helps to enhance the performance of resisting high temperature and shear strength.