Bootstrap approach and Stochastic EM algorithm combination applied for the improvement of the multisource and multi-sensor image fusion process; was presented in this research. Improvement concerned not only image quality and reducing processing execution time as mentioned in our previous Bootstrap EM algorithm (BEM), but also regarding initialization dependence as well as fixed classes' number. Such interesting fusion algorithm for multisource and multisensor image using one stochastic phase, i.e. SEM algorithm, preceded by Bootstrap procedure was successfully implemented and tested for several prototype images. Targeted images were firstly split by an unsupervised Bayesian segmentation approach in order to determine a joint region map for the fused image. The Bootstrap approach was then applied to the targeted multisource image in conjunction with the SEM algorithm, forming hence one Bootstrap SEM algorithm called BSEM. The procedure of such algorithm involved both statistical parameters' estimation from one representative Bootstrap sample of each source or sensor images.Keywords: Multi-source multi-sensor image fusion, unsupervised bayesian segmentation, bootstrap approach, sem algorithm.