When calculating the compression-buckling stability of pile foundation in waterway engineering,the length coefficient of the compression bar in the current code of our country is based on the ideal constraint,but the actual constraint of pile foundation in most waterway engineering is not consistent with the ideal constraint,and the pile top is assumed to be fixed or hinged to be dangerous.Aiming at the above problems,based on the analysis of the actual confined state and stress state of pile foundation,a new limit equilibrium equation is established,and the compression-buckling stability length coefficients under different confined states and different equivalent pile numbers are obtained.The main recommendations are:for most projects,when the pile tip and the pile top are hinged,μ is recommended to be no less than 1.0;when the pile tip or top is fixed and the other side is hinged,the μ is recommended to be 0.80~1.43;when the pile tip and the pile top are both fixed,the recommended value is 0.60~0.72.The conclusion of this paper can provide a basis for optimum design of pile foundation with large slenderness ratio in waterway engineering,and can also provide a reference for revision of appendix to the code.