PM2.5 thermophoretic deposition efficiency in turbulent gas flowing over tube surfaces is analyzed using the new concept of potential capacity and potential capacity variation. According to Romay's model, a thermophoretic deposition efficiency model in turbulent gas flowing over tube surfaces is built up based on the potential capacity. Through computing and analyzing thermophoretic deposition efficiency, PM2.5 thermophoretic deposition efficiency in turbulent gas flowing over tube surfaces in direct ratio to the potential capacity variation and in inverse ratio to the temperature ratio of tube wall to entrance gas-particle mixture. And the imprecise notion of thermophoretic deposition efficiency direct ratio to the temperature difference between tube wall and entrance gas-particle mixture is reviewed. There are credible foundations to be provided for improving and researching thermophoretic deposition efficiency in theory and experiment.