Myeloid differentiation factor 88 (MyD88) is a universal adaptor protein and plays an important role in the signal transduction of Toll like receptors (TLR) family. In this study, the MyD88 gene from the Haliotis diversicolor (hdMyD88) was identified. The full-length cDNA of hdMyD88 has a 1927 base pairs (bp), with an open reading frame of 1314 bp encoding 437 amino acids including a death domain (DD) at the N-terminus and TIR domain at the C-terminus which are typical features of MyD88 family proteins. Three conserved boxes are also found in the hdMyD88, which are similar to MyD88 in vertebrates. The expression levels of hdMyD88 mRNA at different early embryonic developmental stages of abalone were measured by qPCR revealed that their constitutive expression at all developmental stages analyzed with the considerably highest values at 8 cell stage and the lowest level at the trochosphere stage. Additionally, the mRNA expression of hdMyD88 decreased significantly (P < 0.05) after MyD88-dsRNA soak in the stage of trochosphere and veliger than EGFP-dsRNA group and blank control group. Whole embryo in situ hybridization showed that the positive signals of hdMyD88 were in visceral mass of trochophore larvae and veliger larvae. These results indicate hdMyD88 may could respond to pathogenic infection and may play an important role in early innate immunity in the process of abalone larval development.