Recently, the caterpillar Thosea obliquistriga Hering was an increasing important pest of Canna growing at Hungyen and Hanoi. The research was conducted to identify roles of main natural enemies of the caterpillar during 2009-2011. The results showed that the bee fly Systropus macer Loew was the only endoparasistic found from pupae of the caterpillar collected from fields of canna growing at Hung Yen and Hanoi, Red river delta, Vietnam. This bee fly was the first time recorded in the insect fauna of Vietnam. The highets percentage of pupae of caterpillar parasitized by the bee fly at Hanoi in 2009, 2010 and 2011 was 20.6 percent, 21.6 percent and 20.05 percent, respectively. Meanwhile this percentage at Hung Yen was lower.