In order to know the effect of different processing methods on protein digestion of abalone (Haliotis discus hannai), the effects of four processing methods including raw, boiling, canning, and drying on the digestibility of abalone muscular proteins were investigated. Simulated gastric fluid (SGF) as well as simulated intestinal fluid (SIF) was used to study the effects of in vitro digestion. The products were evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Scanning electronic microscopy (SEM) was used to observe the differences in the fiber of the four products. The results showed that the digestibility of proteins in canned abalone was the highest among the four processing methods. Proteins from dried abalone were most resistant to digestion both in SGF and SIF. The four processing methods revealed different fiber structures under SEM. Furthermore, the angiotensin-I converting enzyme (ACE) inhibitory activity of the digested products exhibited the following order: canned (464.2 μg/mL) < dried (665.4 μg/mL) < boiled (775.7 μg/mL) < raw (803.9 μg/mL). In conclusion, our present study suggested that different processing methods of abalone significantly affect the digestibility of proteins and the ACE inhibitory activity of the final products, which may provide a reference for abalone processing and consumption.