Aimed at 6-DOF modular manipulator, singular configurations was analyzed within its workspace. Firstly, modular manipulator system was constructed, and the forward kinematics model was conducted by using the DH method. Secondly, combining the kinematics equation, the Jacobian matrix was constructed by using method based on link speed of manipulator, and all the singular states of the manipulator was solved through the method of singular decomposition, all the singular points within its workspace were acquired and the corresponding configurations were shown. Lastly, simulation analysis of manipulator with singular configurations was completed based on the manipulability flexible index and the minimum singular value flexible index by means of the robotics toolbox, changing of the manipulability, the smallest singular value and the Jacobian matrix rank of manipulator were shown during each joint rotting within its range, and the manipulability ellipsoid of end reference point of manipulator was explored when manipulator was in singular configuration. The simulation results showed that the manipulator had three singular states within its workspace, and the manipulability and the minimum singular value were tended to zero, the Jacobian matrix was rank-reduced and the position manipulability ellipsoid of end reference point of manipulator was reduced to a plane when manipulator was in each singular states above. Simulation results verified the correctness of the singularity analysis, and laid a foundation for subsequent trajectory planning research and singularity avoidance research of modular manipulator.