Application with the development of industrial mechanical arm, the precision and the reliability of position at end of industrial mechanical arm are caught more and more attention.The six degrees of freedom(6DOF) mechanical arm is the research object.The effect was analyzed of parameter error of the position at the end of mechanical armon mechanical arm posture deviation value and the terminal pose reliability.The matrix method was used to build the model of deviation value of position at end of the mechanical arm,and the method of perturbation the model of error is used to build the model of the deviation value.The innovation point is to use MonteCarlo method to calculate each parameters error which caused the deviation value of the pose at the end of mechanical arm and the reliability sensitivity of the pose based on each parameter error.