Abstract: The laboratory study on gelation time and the gel strength of Cr-system and phenolic aldehyde-system of low degree cross-linking has been carried out.The results indicate that under the same concentration of crosslinkers, the higher the concentration of the polymer,the shorter the gelation time and the greater the gel strength;while under the same concentration of polymer,the higher the concentration of the crosslinkers,the shorter the gelation time and the increased greater of the gel strength.Therefore,a twin-tube parallel core experiment using low-crosslinked agent has been carried out.The results show that the low degree of cross - linking can effectively plug the large pores and expand the swept volume of water flooding so as to enhance oil recovery.As a result,the series of low- crosslinked system is recommended in the paper.