Abstract：As a reinforcing material，the geosynthetics is widely used in engineering practice to strengthen the foundation，slope，road，pavement，crushed-stone column，etc.. However，the study on the reinforcement mechanism and the relevant design theory are much backward relative to the engineering application. As a result，the development of reinforcement technology was interfered. The need for studying the interaction behavior between geosynthetic and soil has been realized by Chinese engineers. This paper firstly presents some typical views on the reinforcement mechanism in China. Based on the analysis of those views，the author realized that all the mechanism of reinforcement can be divided into two aspects：(1) the direct reinforcement effect，which is resulted from the contact surface between soil and reinforcement material；and (2) the indirect reinforcement effect，which is resulted from the “composite” soil adjacent to the contact-face. Both effects have the functions of improving rigidity，re-distributing stress and strain fields，changing the failure mode of soil，etc.，particularly，the mechanism associated with shear-band in the soil adjacent to contact-face is discussed. Thereafter，some results from laboratory tests，modeling tests and field observation are presented to show the reasonableness of this new point of mechanics.
