The transparent mutant of Poecilia reticulate was hybrid with wild type for genetic study. The analysis of offspring phenotype showed that the transparent characteristics was recessively inherent, controlled by an allele in line with Mendelism. Stereomicroscopy was used to examine the types and patterns of chromatophores for each phenotype, and it was found that the transparent mutant exhibited loss of iridophore. The paraffin section examination and electronic microscopy on the skin and peritoneum of guppy showed that the transparent mutant had an intact structure of skin and peritoneum, except for the absence of iridophore layer in contrast to wild-type individual. Reflective iridophore was absent in transparent mutant to the penetration of light, resulting in transparent appearance. The mutants were healthy and fertile, showing a stably genetic trait, and the main internal organs, such as heart, liver, gut, gonads, kidney, gills, and spinal cord, were naked-eye visible in living fish. Therefore, the P.reticulate transparent mutant is an excellent experimental resource for in vivo studies.