We studied differences between the size and surface of tongue among three of Old World bats (Pteropodidae, Chiroptera), two frugivorous species (Cynopterus sphinx and Rousettus leschenaultii) and one nectarivorous species (Eonycteris spelaea). The maximum tongue length were measured by two measurements of length inserted into the tube with diameter in 2 cm. L1 (including the snout and the tongue outside snout), and L3 (tongue length outside snout). The maximum of tongue length L1 was 29.19±0.52 mm for C.sphinx, 35.05±0.82 mm for R.leschenaultii, and 49.34±1.64 mm for E.spelaea; L3 in the three species were 16.25±0.53 mm, 19.25±0.79 mm, 31.88±1.56 mm, respectively. The two length measurements were converted with weight and resulted in 8.57±0.17 mm/g^1/3, 7.90±0.27 mm/g^1/3, 12.41±0.40 mm/g^1/3 for L1 in the three species and 4.77±0.16 mm/g^1/3, 4.34±0.22 mm/g^1/3, 8.01±0.38 mm/g^1/3 for L3; the anatomical tongue length after conversion were 5.56±0.16 mm/g^1/3, 5.35±0.14 mm/g^1/3, 6.65±0.38 mm/g^1/3, respectively. There were significant difference in these five variables among the three species, i.e. the value of five variables in nectarivorous bat were significantly longer than those of the other two frugivorous bats. By comparing tongue structure, we found that E.spelaea had a long and tapering brush-tipped tongue with many grooves on the surface and two sides, while the tips of C.sphinx and R.leschenaultia's tongues were blunt and with less grooves and brush structures. Our results indicated that the tongue length and structure between Old World nectarivorous and frugivorous bats were different, which may result from the difference of foraging behaviour.