To study the nonlinear impact of calibration errors on the positioning accuracy of a robot's end⁃effector, a linkage analysis of end⁃effector pose calibration errors for a six⁃degree⁃of⁃freedom robot was conducted. Using the modified Denavit⁃Hartenberg model (MDH) constraints, a kinematic parameter model for a six⁃degree⁃of⁃freedom robot was established to analyze the spatial geometric relationships of the end⁃effector's pose transformation. The sources of robot calibration errors were examined, and the functional relationships between the coordinate systems of the measurement system were derived. Based on this, a calibration error propagation model for the robot's end⁃effector pose was constructed. A calibration system for a six⁃degree⁃of⁃freedom robot was set up to conduct experiments. Experimental results indicate that the primary sources of calibration error in robotic end⁃effector positioning include link length errors, joint offset errors, joint twist angle errors, and zero⁃position errors. The combined calibration error was measured as 2.66 mm, with relative uncertainties in the x, y, and z directions of 0.09%, 0.37% and 0.46% respectively. The research findings provide technical references for achieving precise positioning control of the robot's end⁃effector.