We established an improved method for the determination of four estrogens including estriol (E3), 17beta-estradiol (E2), 17alpha-ethynylestrodiol (EE2) and estrone (El) in water. The method consisted of solid-phase extraction (0.5 L water) and subsequent analysis of analytes by ultra-performance liquid chromatography (UPLC) with an ultraviolet detector (UVD). Base-line separation was achieved for all studied estrogens using a column (50 mm x 2.1 mm) packed with 1.7 microm particle size stationary phase. Recovery was higher than 88% and detection limits ranged between 12.5-23.7 ng/L for the four estrogens, with the RSD ranging from 7% to 11%. The method was successfully applied to determine E2 and EE2 in simulated natural water, which found that about 70% of E2 was degraded (with a half-life of about 30 hr) within 48 hr and about 55% of EE2 was degraded (with a half-life of about 36 hr). Low levels of E1 were found, however E3 was undetectable during the process.