Performance characteristics of partially hydrolyzed polyacrylamide（HPAM）and the pecial viscoelastic Cr3+ cross–linked polymer（CLP, Cr3+ as the cross linker）solution were investigated by the measurement of the viscosity, viscoelasticity, polymer coil dimensions, molecular configuration, flow characteristics, and profile modification using the Bush viscometer, rheometer, dynamic light scattering system and core flow device. The results showed that, under the same polymer solution, intra-molecular cross–linking reaction and inter-molecular cross-linking reaction could take place when the cross-linking agent concentration was proper. The intra-molecular cross-linked would make the viscoelasticity of the system increase obviously. Compared to the polymer solution with the same concentration, the viscosity of intra-molecular cross-linking polymer gel was similar, while the viscoelasticity were a little bigger, and the d rag coefficient increased by 50 times, and the residual resistance coefficient increased more than 100 times, and the oil recovery of the intra-molecular cross–linking polymer gel increased by 6.2%.