Abstract: We studied the echolocation of Thylonycteris pachypus and T.robustula in southern Guangxi,China,which were often found roosting within internodes of the bamboo (Bambusa spp.).The echolocation signals of the T.pachypus and T.robustula were compared when the bats were flying in the laboratory.The result revealed that the echolocation calls of both T.pachypus and T.r bustula were FM signals.The frequency range of T.pachypus was higher (62.4-91.6 kHz) than T.robustula (42.7-72.4 kHz),the dominant frequency of T.pachypus was also higher (76.5±2.1) kHz than T.robustula (49.2±1.8) kHz.But the pulse duration is not significant difference,nor do interpulse interval,repetition rate and duty cycle between the two kinds of bats.The characteristics of the echolocation calls of the two bats perh aps made them adapt to their bodysize and micro-habitat.