PIWI-interacting RNAs(piRNA) are endogenous small RNAs(sRNA), which play roles in resisting exogenous gene invasion and transposon mobility. More than 16 000 piRNAs are found in Caenorhabditis elegans, and the piRNA loci share a conserved upstream sequence. New piRNAs can be predicted based on its conserved upstream sequence. C. elegans are synchronized and small RNAs from wild type and prg-1 strains at L4 developmental period are sequenced through illumina technology. Basing on piRNA conserved uptream sequence, we find 967 new piRNAs expressed at L4 period, and the expressions of new piRNAs disappear in prg-1 mutant. Most of new piRNAs are mapped into two piRNA clusters of Chromosome Ⅳ, and have an overwhelming bias for a 5' uracil. Compared to the published co-immunoprecipitation data from adult worms, over 100 new piRNAs can interact with PRG-1. However, some non-21nt long sRNAs, which also share the same loci with piRNAs, are also found in wide type worms. These non-21nt long sRNA may be co-products of piRNA precursors. Together, these results indicate that our sRNA sequencing identified many new piRNAs in C. elegans.