The crystal structure of the partly deuterized triglycine sulfate was studied by four-circle neutron diffractometer. The result is compared with TG-S data obtained by Kay et al. The distance between triglyeines groups increases hlightly by deuterization, The relative increases of lattice parameters a, b and c are 0.47%, 0.50%, 0.19%, respectively. The probability of deuterium substitution, P, on various hydrogen sites is obviously divided into two classes; P=0 for hydrogens locked in C-H bonds, while P= 0.84±0.03 for all the others.