Abstract: Steinernema litorale and Steinernema ceratophorum were isolated from a soil sample collected from Harbin of Heilongjiang province and identified by molecular approach. The results of PCR amplification and sequence analysis of these two Steinernema internal transcribed spacer (ITS), indicated that the fragment length of ITS region of S. litorale and S. ceratophorum were 913 and 1000 bp, respectively. There is no report about symbiotic bacteria of S. litorale research. So we isolated and identified its symbiotic bacteria through amplifying 16S rDNA fragment, the symbiotic bacteria of S. litorale was Xenorhabdus bovienii with 1388 bp and the symbiotic bacteria of S. ceratophorum was Xenorhabdus budapestensis with 1517 bp. In order to clarify S. litorale and S. ceratophorum vitality in the alpine region, we analyzed the infectivity of the both symbiotic bacteria to infest Galleria mellonella. The results showed that the G. mellonella larvaes no died when they were infested the four kinds nematodes at 5℃ condition for 144 h. G. mellonella infected by S. litorale was significantly higher molitaly than other EPNs at 10℃, the corrective mortality of G. mellonella larvae being treated for 96 h was 85.83%, and the other three treated corrective mortalities were 0 (P<0.05)；at 15℃, S. ceratophorum appeared an relatively high infectivity, the corrective mortality of G. mellonella larvae being treated for 72 h was 89.17%, and S. litorale did not die after treating G. mellonella larvae for 72 h, and started to die after treating G. mellonella larvae for 96 h, and its corrective mortality was 87.5%, the corrective mortality of S. ceratophorum after treating G. mellonella larvae for 96 h was 96.67%，S. ceratophorum appeared relatively high infectivity than the other two treatments, however, while comparing to S. litorale, there was no significant difference between them.