Ultrafine diamond powder prepared by explosive detonalion is a new assortment of synthetic diamond.In this work, underwater explosion of cast TNT/RDX 50/50 charge was used for the preparation.An improved method is that the explosion synthesis can be carried out subsepuently one times and more in the same batch of water in the explosion chamber.Expeimental results revealed that the products prepared by continuous multiexplosion up to 9 times gives nearly the identical XRD and TEM graph and IR spectra as those of the product preparcd by single expolsion.The total yicld of diamond powder does not decrease as well.All of the experimental results indicate the multicxplosion method has no harmful influencc on the particlc size and structure of diamond powder,while the procedure is much more simplifed and production efficency is obviously enhanced.