Human motion capture typically requires synchronization hardware and specialized cameras, which makes the system expensive and technically complex. Instead, in this paper, we propose a novel approach for markerless motion capture with multiple unsynchronized cameras. Cameras synchronization is achieved using sharp illumination changes produced while recording the videos. To estimate poses with the presence of sharp illumination changes, we also propose a pose estimation method based on a bilayer Gaussian Mixture Model (GMM) and graph-cut, which can handle sharp illumination changes. And we demonstrate our video synchronization and markerless motion capture methods by the experiments on real human motion videos.