A new commercial cultivar ‘Hae Sal’ of Hypsizigus marmoreus was developed by the method of mono-mono crossing between monokaryotic strains derived from KNR8047 and KNR8080. The parental strains are characterized by the property of high quality and a short period of time in cultivation respectively. The optimum temperature of mycelial growth was 25°C and that of fruiting body development was 15~16°C. The period of harvesting including primordia formation was 7.0 days shorter than that of control strain ‘Mangadak No.2’. The color of pileus and stipe surface was neutral-brown and pure white, respectively. The yield was 117.6±23.2g/850cc plastic bottle. Analysis of the genetic characteristics of the new commercial cultivar ‘Hae Sal’ showed a different profile as that of the control strain, ‘Mangadak No.2’, when RAPD (Random Amplified Polymorphic DNA) primer was used. This new cultivar ‘Hae Sal’ of Hypsizigus marmoreus is characterized by the improved quality and a short period of time in cultivation after scratching. It would be of much help to expand the cultivation area of Hypsizigus marmoreus.