Abstract: To meet demands of exploiting the horizontal well, it is of great significance to develop downhole tools that possess independent intellectual property, study the Sondex downhole tractor in the international leading level and improve it according to domestic practice. This article first introduces the domestic development of new logging technology and downhole tractor for horizontal wells, analyzing the deficiency and limitation. The article continues to analyze the features of Sondex downhole tractor for horizontal wells including the structure, working principle, performance parameter, composition and realization of control system and driving mode, with emphasis on principle, structure and performance parameter. The article describes the characteristics and application of Sondex tractor in detail, which provides the technical support and a new idea for design and development of downhole tractor tool for horizontal wells.