The invention belongs to the relevant technical field of the fatigue life calculation of a metal structure, and discloses a fatigue life assessment method based on an engineering machinery structure.The method comprises the following steps that: carrying out finite element analysis on the engineering machinery structure, and combining with a practical operating situation to determine a fatigue dangerous area; carrying out a dynamic stress testing experiment to obtain the stress time history of the fatigue dangerous area in multiple practical operating circulations; carrying out rain-flow counting, average stress correction and equivalent damage conversion on the stress time history in each operating circulation in sequence to obtain equivalent stress and equivalent circulation frequency corresponding to each operating circulation; and for the equivalent stress and the equivalent circulation frequency obtained each time, through a nonlinear cumulative damage theory, calculating the cumulative damage and the fatigue life of a bucket rod structure. By use of the method, the rain-flow counting method and the nonlinear cumulative damage theory are organically combined, the influence ofa loading sequence between the operating circulations is considered, a calculation process is simplified, calculation accuracy is improved, and the method is suitable for engineering application.