It is assumed that horizontal displacement of pile has a longitudinally cubic power function, and equivalent-moment finite element-iterative method which can analyze the P-Δ effect of piles under inclined and eccentric loads, is derived in the paper. And matlab process of equivalent-moment finite element-iterative method is edited. Case analysis is done in the paper for displacement and stress calculation of pile under inclined and eccentric loads, moment, pile gravity, horizontal distributed loads, vertical distributed loads, scattering vertical forces and soil-pile friction. Finally conclusions are drawn as follows: (1) equivalent-moment finite element-iterative method is proved to be a effective method for P-Δ effect analysis of piles under complex loads; (2) P-Δ effect is notable while piers are high.