—This paper presents an online method for a cooperative mobile robots navigation using local robot's reference frame. The group of robots must navigate while keeping a geometric shape. To achieve with distributed and reactive way the Multi-Robot Formation (MRF), a cooperative object detection using range data is presented. This information will permits to detect the position of the leader robot in the formation. Indeed, in this work it is proposed that the leader can be surrounded by an ellipse and its parameters are obtained online using the sequential range data from all the mobile robots. An appropriate method is used to identify the enclosed ellipse. To perform the MRF, it is proposed to use a combination between behavior-based, dynamical virtual structure (already presented in [1] which use global reference frame) and leader-follower approach. Simulations will permit to show the efficiency of the proposed reactive and distributed cooperative navigation.