Abstract: The semi-conductive buffer water blocking tape for high voltage cable has been used for many years, but its performance research is rarely reported. The performance of water blocking tape made by excellent manufacturers in the market was studied, and its water absorption, electrical performance, mechanical property and aging performance were tested. The results showed that: with the increase of aging temperature, the elongation and strength of the water blocking tape also had an increasing trend; after aging, the water absorption expansion of the sample changed greatly, and B basically losed the water absorption function when aging at 135 ℃; in general, sample B performs better at 90 ℃; samples A and C had too high resistance, and the water absorption capacity and electrical properties changed obviously after aging.