Water-soluble CdTe nanocrystals welag prepared in the presence of 3-mesaptopropionie acid (MPA).By adding additional Cd2+ or poly (acrylic-acid)(PAA) to the solution,aggregates of CdTe nanocrystals were obtained．and their size varied with the amount of Cd2+ or PAA．Cd2+ or PAA have an important effect on the aggregation process of CdTe．Additional Cd2+ can accelerate the formates of aggregates by linking with earboxyl on different CdTe particles,while PAA also acts as a linker between CdTe particles．When the freshly prepared nanocrystal salutions were stored for a long time,the interaction between the carboxyl and Cd2+ on different particles would lead to the formation of CdTe aggregation．The aggregation process was also a process of surface passivation which led to the dmmatical increase of photoluminecence intensity．These results showed that the size of the aggregates could be contmned by adjusting various conditions of aggregation．