This study was carried to develop new white cultivars that are suitable export using back cross method of Hypsizygus marmoreus. At first, we did select mother strains(Hm3-8 as brown and Hm0-7 as white) that have excellent cultivational caracteristics and morphology. The two strains are collected spore and selected 150 monokaryon mycelia by dilution method, and then picked out, 10 monokaryon strains, that havn‘t clamp connection and different mycelial morphology on plate. The selected monokaryon mycelia of GPHm3-8 and GPHm0-7 was crossed in PDA plate and the, acquired 100 dikaryon strains as mating rate is 100%. The 100 dikaryon strains is cultivated by sawdust media. And, we are selected 5 strains (BW16, BW41, BW56, BW76, BW96). To practice back cross, we selected 10 monokaryon mycelia that didn't clamp connection from the 5 stains(BW16, BW41, BW56, BW76, BW96). And then, we were carried out back cross with Hm0-7. The mating rate were investigated 31%, 33%, 33%, 34%, and 47% within BW16, BW41, BW56, BW76, and BW96, each other. We obtained 15 hybrid strains as brown line, and 23 hybrid stains as white line among 178 hybrid strains, and picked up 23 white strains because 15 brown strains were not suitable our object to develop new white cultivars among 38 strains. To select the best white strain , cultivated by standard growing condition, and BW76W-13 strain has been selected because it had good quality and morphology, finally. We were carried RAPD to verify difference between mother strains. We confirmed that band pattern of BW76W-13 had different pattern compared with mother strains.