The first part of the paper describes the mechanical structure of RTTRR small-sized modular robot. The second part is reserved for the determination of the geometric model of the robot, using the method of rotation matrices [2] and the third part presents the kinematic model, determined using the iterative method for kinematic modeling [2]. The equations of the geometric and kinematic models are determined with the help of the first three modules of the generalized modeling application Robot_Symbolic [1] and they are useful in the simulation of the geometric and kinematic behavior of the analyzed robot.