Abstract: Distributed through-the-wall imaging radar (DTWIR) deploys multiple through-the-wall radar nodes in multiple viewpoints for cooperative detection of indoor targets, which can effectively compensate for the shortage of traditional single-view through-the-wall target detection. In this paper, a registration algorithm for DTWIR is proposed, which calculates the positions of the radar nodes based on their detection results. Firstly, the measurements of each radar node are modeled as Gaussian mixture model. Then an optimization problem which solves the optimal coordinate transformation parameters is formulated for radar registration. Finally, the optimization problem is solved via the particle swarm optimization method. The proposed algorithm is validated by simulation and experimental results.