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.