Weak gel with PAM cross-linked radical reaction was prepared by being incorporated to side chain of PAM. The structure, gel for ming process and the influence of NaCl concentration to apparentviscosity of gel were studied. The results show that the crosslinking ratios influence to crosslinking time, gel breaking time and gel strength. The crosslinking time decreases and gel strength slightly increases with increase of crosslinking ratio. Apparent viscosity of Polyacrylamide derivative crosslinking system increases with increase of NaCl concentration. The weak gel has good salt tolerance ability.