Abstract: An effective algorithm DMEO applying the deferred-merge embedding (DME) algorithm is presented for clock tree construction in the presence of obstacles.During the clock routing,a track graph is constructed in order to guarantee the obstacle-avoidance.By considering obstruction as routing constraint,the method is composed of a bottom-up phase computing possible loci of nodes and a top-down step to determine the exact placement of each node in the clock topology tree.Experimental results show that the algorithm is promising with more than 7% wirelength reduction.