Abstract: To study the conductive error of straight sensor, a special sensor was designed, which can measure 3 points- temperature, air flow, downside and upside of the bracket. The first and the third point were movable to meet the need of study. The theory model was set up and conductive correct coefficient formula was deducted. To avoid the influence of radiation error, a method of boot-heating was adopted to study the influence of Ma, bottom temperature and long-diameter ratio to conductive error, and useful datum were received. Conductive correct coefficient formula was applied to calculate conductive error of high-temperature-water-cooled harrow when the air flow velocity was low (Ma=0.1). The relative error was little than 10%. It pointed out that when considering the conductive error on temperature measurement, it is not comprehensive that whether long-diameter ratio is larger than 10 or not, bottom temperature is also an important thing.