The production of hybrid onion (A. cepa L.) seed is economically feasible using systems of cytoplasmic male sterility (CMS). Therefore, male sterile (A-line) and maintainer (B-line) is essential to development of F1 hybrids. Male sterile line Wonye30006’ was developed by Bioenergy Crop Research Center, National Institute of Crop Science, RDA in South Korea in 2010. The first cross for introduction of CMS was conducted in 2000. Male-sterile parents which were selected from ‘F2-6’ breeding lines were pollinated with male fertile line ‘HMB’ (inbred line). The fertility test was conducted in 2002 and maintainer line ‘Mo2005’ was selected. The proportion of male-sterility plants of F1 population was 100% for subsequent four backcross generations. ‘Wonye30006’ was named ‘MMS66’ in 2009 and the corresponding male parent was called ‘MMSB66’. As an mid-late maturing type, lodging date is around May 25^th. ‘Wonye30006’ has round bulb and the average bulb weight is 184 g. Plant height and stem diameter are 56 cm and 12.4 mm, respectively. Number and the length of flower stalks per mother bulb are 122 cm and 6, respectively. Flowering date is June 4th and flower bud size is 81.2 mm. Wonye30006 will be used for development of F1 hybrids in breeding program. (no. 4674)