Abstract: To test the most suitable temperature and illumination for the egg hatch of duck Cyathocotyle caecumalis sp.nov, the hatch trail was set up as 5groups under the conditions of 3hours′sunshine per day with different room temperatures (28³6℃, 20²8℃, 10²0℃ and 0¹0℃) as well as a constant temperature of 27℃ with no sunlight.The results showed that the egg hatchability of the groups of 28³6℃ and 20²8℃ were 27.5% and25.2%, whose hatching time were 14 days and 21 days, respectively;while for the group of 10²0℃, eggs developed poorly:the hatchability was 5%and the hatching time was 28days;and none egg of the group of 0¹0℃developed;as to the group of constant temperature 27℃ with no sunlight, the eggs merely developed and most of the miracidias died.This trail indicated that the most suitable condition for the egg development of duck Cyathocotyle caecumalis sp.nov was the temperature of 20³6℃ with more than 3hours′sunshine per day.