Abstract: The criteria for screening the polymer?gel system was laid out according to the high temperature reservoir conditions of Hejian Dongying oilfield. A suitable HPAM/Phenol Formaldehyde gel system was screened from the five candidates based on the criteria. Orthogonal experiments were carried out using the30?day viscosity value and the average retention rate of the gelled system as evaluation indexes. The order of the factors influencing gelling strength and long?term stability is as follows: polymer>cross linker>assistant agent. Finally, the best formula (1200mg/L of polymer+2250mg/L of cross linker+1750mg/L of assistant agent) was determined based on the formulation optimization experiment. As of the midmonth of December in2014, the pilot tests have been carried out in ten well groups, of which six wells preliminarily became effective and seven wells obviously effective. The average wellhead pressure was increased by5.32MPa and the cumulative incremental oil production was1262tons