Aimed at BH heat-resistant polymer, 4500mg/L solution is compounded by oilfield sewage, and then diluted into 1500mg/L solution by oilfield sewage again under room temperature, aging in the constant temperature box of 95°C finally. Test slides are made of different aging time BH heat-resistance polymer solution, whose thermal stability is manifested by atomic force microscope. Results show the aggregation degree of BH heat-resistant polymer solution are different after aging for 30d, 60d, 90d under 95°C. They gather largely before aging, are into a loose branch distribution. After aging for 30d, their aggregation degree declines, branch length becomes shorter. After aging for 60d, their aggregation status change greatly, are into "╫╫" shape comb distribution. After aging for 90d, they gather into about 10μm in diameter short fat wafer, and are not easy to expand.