Most of the cyanophages were adsorbed onto the ultrafilter membrance when pre-filtrated water sample passed through the tangential flow ultrafiltration system. In order to recover much more cyanophages, we used a technique named "backflushing ultrafiltration". The results indicated that when the volume of the backflush liquid was raised step by step, the concentration multiple of the cyanophage would gradually decrease, while the recovery rate of the cyanophage would gradually increase. In our performance, the maximal concentration multiple and the recovery rate of cyanophage could reach up to 30 times and more than 90% severally. This method was tested to be effective for concentrating cyanophage from large volume liquid sample. Moreover, the concertration multiple of the cyanophage could be elevated to nearly one-hundred times when two-step backflushing ultrafiltration was adopted