Abstract: Taking Xinyang red clay as the research object,3％,6％,9％,and 12％lime and tea seed shell ash were added to improve it.The improvement effects of the two materials on red clay were compared and analyzed through boundary moisture content test,direct shear test,unconfined compression test,compression test,and electron microscopy micro scanning.The experimental results showe that:(l)The addition of lime and tea seed shell ash can affect the plastic limit,liquid limit,and plastic index,and the degree of influence is in order of plastic index plastic limit and liquid limit.(2)The addition of 9％lime can effectively improve the engineering properties of red clay.(3)The mechanism of lime improving red clay is that CaO and active substances in the soil generate Ca(OH)2,calcium silicate hydrate(C-S-H),calcium aluminate hydrate(C-A-H)and other gel substances,and gel substances wrap the soil particles,making the soil microstructure compact,resulting in the improvement of soil strength.(4)The chemical composition of tea seed hull ash did not react with the active substances in red clay to form gel,and its improvement effect was weaker than that of lime.