The paper first analyzes the working principle of the precision two-axis mechanical arm and designs a highly accurate and rigid two-axis mechanical arm structure.Secondly,it calculates and verifies the servo motors and reducers for the upper arm and forearm,determining their models.Simultaneously,it selects and calculates the model of the angle encoder at the output end of the mechanical arm.Finally,through the development of a precision two-axis mechanical arm and actual testing,it verifies that the torsional rigidity of the actual output end of the reducer is close to the theoretical values.