Objective To know the contamination status of Giardia lamblia and Cryptosporidium in drinking water of Jiangsu Province,so as to provide the evidence for producing hygiene and safety drinking water. Methods A total of 28 water plants of 13 cities in Jiangsu Province were selected,and the source water(10 L),chlorinated water(100 L)and tap water(100 L) were collected separately in each site. The water samples were then treated by filtration,washing,centrifuging concentration, immune magnetic separation,and immunofluorescent assay,to detect the numbers of Giardia cysts and Cryptosporidium oocysts. Results Totally 84 samples from 13 cities were collected,including 28 source water,28 chlorinated water and 28 tap water samples. Among the chlorinated water and tap water samples,no Giardia cysts and Cryptosporidium oocysts were found. Howev-er,Giardia cysts were detected in 3(10.71％,3/28)source water samples(Yancheng,Lianyungang,Changzhou cities),with the density of 1 cyst/10 L of all. Cryptosporidium oocysts were also detected in 3(10.71％,3/28)source water samples(Nan-jing,Zhenjiang,Yangzhou cities),with the density of 1 oocyst/10 L of all. Conclusions The source water in partial areas of Ji-angsu Province has been contaminated by Giardia and Cryptosporidium. To ensure the safety of drinking,the regulation of source water and surveillance of drinking water should be strengthened.