To investigate the distributive pattern and morphological characteristics of mast cells (MCs) in Pachyhynobius shangchengensis , MCs from digestive system and some of other organs were observed by using different fixatives and staining methods, then cell numbers in digestive tract and tongue were counted and analyzed statistically. The results indicated that improved toluidine blue staining (MTB) could be used to display MCs in all organs except for the Fallopian tube and kidney in 3 fixatives, but Alcian blue-Safranin O staining (AB-S) displayed AB⁺ MCs and S⁺MCs in digestive tract and only AB⁺ MCs in other organs. The shape of MCs was round, ellipse, long-shuttle, linear or irregular. The MCs tended to be adjacent to blood vessels and glands. Numerous MCs were found in tongue, esophagus, stomach, skin, the combining site of uterus and the Fallopian tube, and a few in mesentery, liver, pancreas, muscle, uterus, small intestine, duodenum and rectum. Evidently, different from background color (blue), MC plasma in MTB was purple, red, bluish violet and the outline of MCs could be observed clearly, whereas MCs in AB-S was blue (a few red MCs in digestive tract), with the background poorly stained. These data show that MCs exist in most tissues of P.shangchengensis , and that toluidine blue better stains mast cells.