The aim of this work was to determine bioavailability and in vivo calmodulin-dependent-phosphodiesterase (CaMPDE)-inhibitory activity of six flaxseed-protein-derived peptides (AGA， AKLMS， QIAK， RWIQ， QQAKQ， and KQLSTGC) after oral administration to Wistar rats. Initial experiments tested the cytotoxicity and cellular-transport potentials of the peptides using Caco-2 cells. The cytotoxicity assay indicated that none of the six peptides had an adverse effect on the proliferation and viability of the Caco-2 cells， whereas the transport assay confirmed peptide translocation across the cell membrane. However， only two of the peptides (AGA and RWIQ) were detected in the rat serum up to 90 min postgavage， with traces of RWIQ persisting in serum 1 week after oral gavage. The six peptides inhibited plasma activity of CaMPDE with AGA (34.63%)， QIAK (36.66%)， and KQLSTGC (34.21%) being the most effective 30 min after gavage. In contrast， only AGA maintained significant plasma-CaMPDE-activity inhibition (44.35%) after 60 min.