The invention discloses a mechanical arm space trajectory optimization method for optimal time under multiple constraint conditions. The mechanical arm space trajectory optimization method comprises the steps that firstly, path points of a joint space are generated according to path points in a Cartesian coordinate system of a mechanical arm; secondly, multiple spline interpolation functions of all joints from a task start point to an end point are generated according to the path points of the joint space, and adaptability functions of all the joints are generated according to the constraint conditions; and thirdly, the movement time of all the joints is optimized through an improved Chaos particle swarm algorithm, and an optimal solution is finally obtained. According to the mechanical arm space trajectory optimization method for the optimal time under multiple constraint conditions, multiple constraint conditions such as the velocity and the acceleration of all the joints of the mechanical arm are comprehensively taken into account, improvement is conducted on the basis of the particle swarm algorithm, a particle swarm can be switched between a chaos state and a stable state, thestates of all particles are detected, the particles can achieve separation in time when the particles reach the local extremum, and then the diversity of the whole particle swarm is improved. By means of the method, the movement time of the mechanical arm can be effectively shortened under the multiple constraint conditions, and the working efficiency is improved.