Abstract: In normal bunching mode of single drift buncher, the injecting energy of ion beam is strictly re-quired to match the length of drift tube. That restricts seriously the bunchable ion species. In the paper.a method, so called "Nonstandard Bunching Mode" is discussed. By this mode, much more ion speciescan be bunched in the same geometry of single drift buncher and in the same ability of the RF powersupply. For HI--13 tandem accelerator, the modulating bunching voltage and the pulse FWHM at thetarget are calculated for various ion species.