With the rapid advances of wireless communication and positioning techniques, tracking the positions of mobile objects is becoming increasingly feasible and necessary. Traditional spatial index structures are not suitable for indexing mobile objects because of numerous updating operations. A coordinates-organization hybrid-feature indexing structure called C²OR-Tree is firstly introduced in this paper to index the current positions of the hierarchically organized mobile objects. Based on C²OR-Tree, a notable activated-insertion and deferred-deletion (AIDD) algorithm is presented to deal with the bulk updates of the objects coordinates. In view of the local reconstruction characteristic of the C²OR-Tree, AIDD algorithm gives an efficient implemention of the bulk updates with the integration of the insert processing of the updated objects and the earmark processing of the updated regions. Experiment shows that C²OR-Tree can preserve its satisfying query response capability even after many times of AIDD operations.