Abstract: A model test for piles located in steep slopes has been conducted based on similarity theory. The transfer of axial loading, and the identification of critical buckling load have been investigated. The theory calculation formula and the fitting formula of critical buckling loads were obtained. The results show that there is no obvious inflection in the relationship between load and displacement. The buckling failure mode is thus dominant. Further, larger vertical and horizontal displacements of the pile top is observed in long piles. The critical buckling load simultaneously depends on the vertical and horizontal displacements of the pile top. In addition, the larger inclination the slope or the longer the free section of the pile result in smaller critical buckling load, and smaller vertical bearing reduction coefficient.. The comparisons shows that the result from the theoretical calculation and the fitting formula both agree with the result of model tests, and the maximum error is less than 10%. The rationality of the model tests, the calculation theory and the fitting formula is verified. These can provide references for the practical engineering design

Key words: in-slope pile, buckling, model test, critical load, slope effect