Abstract: Hypocrellin A(HA) is easy to dissolve in organic solvent,but difficult to dissolve in water,which has been a bottleneck problem on the application of HA.Thus a new water-soluble fungicide HA-TX-100 micro-emulsion(ME) was developed by embedding HA in Triton X-100.The light & thermal stability and the antimicrobial activities of HA-TX-100 ME were investigated under laboratory conditions.The results showed that HA-TX-100 ME had good stability when the temperature was 0-54 ℃ and the light intensity was below 3 600 lx.Moreover,when the light intensity was 7 200 lx,50 mg/L HA-TX-100 ME showed high antimicrobial activity against Botrytis cinerea,Lecanosticta acicola,Sclerotinia sclerotiorum and Fusarium graminearum,and the inhibition rates were all over 50%.The fungicide had the best inhibitory effect on S.sclerotiorum with inhibition rate reached 77.60%.The protective and therapeutic inhibition rates of 1 000 mg/L HA-TX-100 ME against B.cinerea were 72.05% and 64.73% respectively,which were significantly higher than that of carbendazim wetable powder under the same condition.The results of present study showed that HA had the potential to be developed as photoactive pesticide.