Abstract: While as much as transgenic pest-resistant cotton cultivation economically benefits humanity, it also affects ecosystem bio-safety. Studies have shown that earthworm improves soil fertility via enriching soil physical and biological properties. However, few studies have reported on the effects of transgenic pest-resistant cotton on soil earthworms. This work studied the effects of transgenic pest-resistant cotton on the growth, reproduction and superoxide dismutase (SOD) activity of field-fed earthworms (Eisenia foetida). The five treatments of the experiment included 100 g cow manure + 500 g soil (CK), 50 g transgenic cotton leaf + 550 g soil (50T), 100 g transgenic cotton leaf + 500 g soil (100T), 50 g non-transgenic cotton leaf + 550 g soil (50NT), and 100 g non-transgenic cotton leaf + 500 g soil (100NT). Results showed similar varied trends in the body weights of earthworms fed on the same doses transgenic and non-transgenic cotton leaves. In general, the body weights of earthworms fed on 100 g cotton leaf (100T and 100NT) were higher than those fed on 50 g cotton leaf (50T and 50NT) and cow dung (CK). At the end of the experiment, however, the body weights of earthworm fed on 100 g transgenic cotton leaf dropped to 23.8% of the previous measurement. There were no significant differences in numbers of earthworm cocoons (0~27) and new earthworms (0~57) between earthworms fed on the same doses of transgenic and non-transgenic cotton leaf. However, the number of new earthworms fed on 100 g transgenic cotton leaf (100T) was lower than those for the other treatments. For the most incubation period, SOD activity of earthworms fed on transgenic cotton leaf was not significantly different from those fed on the same doses of non-transgenic cotton leaf. At the end of the experiment after 201 days, SOD activity of earthworms in the 50T and 50NT treatments were significantly higher than those in the 100T and 100NT treatments.