In order to study the effect of acid and alkali pollution on the mechanical properties of red clay, laboratory tests (consolidation test, triaxial test (UU) and direct shear test (quick shear)) have been carried out of the red clay of Yanshan, Guilin, and the samples are soaked in acid solution (HCl) and alkali solution (NaOH), respectively, to get the changes of compressibility index and shear strength index of the red clay by acid and alkali pollution. Two factors, the concentration of both acid(0,1%, 4%, 8%) and alkali (0,4%, 8%, 12%) and the same curing time (7 d, 14 d) were taken into account. The results show that:1)the compression modulus, cohesive force and internal friction angle of red clay soaked in HCl or NaOH gradually decreased, and the extent of which became greater with the increase of acid or alkali concentration and curing time;2)under the same curing time, the degree of change of compressive modulus and cohesion of the red clay soaked in HCl is more significant than that of the red clay soaked in NaOH, and the case was just the opposite in terms of the internal friction angle;3)with the increase of curing time, the cohesion and internal friction angle of red clay soaked in NaOH has greater degree of change than that of the red clay soaked in HCl, and the case was just the opposite in terms of the compression modulus. The analysis of the test results indicate that the chemical composition, particle size and shape of red clay will be changed under the action of acid and alkali solution, which will bring changes to the original stable structure state and weaken the mechanical effect of red clay in Guilin area.