Helicopter trim analysis is essential for helicopter rotor dynamics investigations. The core of it is the solution of high dimensional nonlinear equations. For the advantages and disadvantages of classical methods and intelligent algorithms, a new particle swarm optimization(PSO) method for nonlinear equations is proposed. According to the idea of simulated annealing(SA), Levenberg-marquardt(LM) operator is embedded in PSO. The method takes full advantages of above three methods, solving the problems such as initial value sensitivity of LM and falling into local extreme value of PSO. UH-60A helicopter trim proves the accuracy of the helicopter trim model. On this basis,experimental results of UH-60A helicopter in a certain forward flight, compared with other methods in convergence reliability and solving efficiency, show that the proposed method has reliable convergence probability and high computation rate. It proves the reliability and the practicality of method in dealing with helicopter dynamical problems.