Brood parasitism is a model system of studying co-evolution, however, which species can be parasitized by cuckoo is not clear until now. In order to make sure whether the Pygmy Wren Babbler (Pnoepyga pusilla) can be parasitized by Lesser Cuckoo (Cuculus poliocephalus), we used field observations and molecular analysis to examine it in Sichuan, China. During July, 2015, we found one nest of Pygmy Wren Babbler with brood parasitism (Fig 1). With polymerase chain reaction, two genetic barcodes (cyt b, COI) were successfully amplified and sequenced, 1 012 bp and 680 bp were got for each barcode. The sequences we blasted in gene bank showed the parasite was Lesser Cuckoo, the host was pygmy wren babbler, with 100% ident. With literature search, we found that 10 species, except pygmy wren babbler, have ever been recorded as host of Lesser Cuckoo (Table 1). This study confirmed the existence of the Lesser Cuckoo parasitizing Pygmy Wren Babbler nest.