Abstract: The "Ventilating Odor exhausted Pest free Latrine",have been built based on the design with a sound user's feedback.According to the observation,the latrines,which are up to the requirements of the design,can 100% trap and kill the flies in the latrine,and 98% of the maggot can not grow into flies,and they die in the trough eventually.The writer further researched into the mechanism of the latrine to trap and kill the flies,and found the best lighting ratio and absolute lighting difference needed to trap and kill the Mega Head Aureo Flies(“MHA Fly”,a kind of flies).The light in the trough should be 300 lux stronger than the light in the hall,and the lighting ratio of the hall to thatot the trough should be over 1:1 68.The writer also found that when the light in the hall is more than 600 lux,the latrine performs badly to trap the flies using the lighting difference;when the light in the trough becomes brighter(close to the outdoor natural light),the latrine traps more flies and more maggots can be found in the waste liquid in the trough,and the flies' phototrpism becomes more active.In the meantime,the writer found that the water proof dry maggot blocking structure installed in the trough can prevent the maggots from using the liquid to perform the tension movement,therefore the maggots fail to crawl out and grow into flies,and they die in the trough.The writer suggests that the similar phototropism device can be made and installed in the relevant surroundings to trap flies.We can use the device to kill the flies and maggots in the living surroundings.Also we can use the device to exchange the trashed organic protein into the protein of the files for the animal feed or the industrial purposes.The waste can be turned into profit.