Surface tension is one of the most important factors directly determining transmission capability of heat. An experimental system was improved to measure surface tension of high temperature molten liquid with pulling escape method derived from the du Noüy ring method. Instrument coefficient was calibrated with chemically pure LiNO3. By measuring surface tensions of NaNO3 and Solar salt (60% NaNO3

40% KNO3

mass fraction)

reliability of experimental system and method was validated. On this basis

four samples of quaternary bromide salts from KBr

LiBr

NaBr and CaBr2 were made with different mass ratios. Surface tensions of samples were measured with the experimental system in the temperature range 350—500℃ and fitted as functions of temperature. The results indicate that surface tension values of quaternary bromide salts diminish linearly with increasing temperature

in accord with surface tension change of known molten liquids.