Purpose: Up to now, more than 1048 human miRNAs have been identified.However, the recognition of new human miRNAs becomes more and more difficult.Ionizing radiation, such as X-rays, γ-rays, and heavy ion beams, causes cellular damages, signal transduction, DNA repair, cell cycle checkpoints, and apoptosis, in which many miRNAs take part.Therefore, we hypothesize that some miRNAs which rarely express under normal conditions may increase their expression upon irradiation.Materials and methods: Total RNAs of HeLa cells were isolated 1 h after exposure to 2 Gy of X-rays, and totat small RNAs were enriched by using PAGE, then sequenced by using Solexa technology.Results: Finally, 421 kinds of known miRNAs and 337 kinds of unknown sequences were identified, among which 11 novel miRNAs were characterized by bioinformatic ways and verified by qRT-PCR.Furthermore, putative targets of these miRNAs were predicted by TargetScan software and compared with known proteins down-regulated by radiation.It was confirmed that some of the targets of these novel miRNAs were radiation-related proteins.Conclusions: These results imply that these 11 novel miRNAs are radiation-related miRNAs.This study reveals a new way to find novel miRNAs.