The segmented poly(urethane urea) copolymers were synthesized by one- and two-step polymerization procedures. The copolymers were based on 4,4’-diphenylmethane diisocyanate, 3,5-diethyltoluene diamine, and ethylene oxide-capped poly(propylene oxide) diol. The mean sequence lengths of polyurethane soft block and polyurea hard block as well as the sequence distribution of the hard block in the copolymers were estimated from the signals of aromatic carbons in C-13-NMR spectra. The results indicated that two-step polymerization led to longer mean sequence lengths and broader hard block sequence distribution than one-step polymerization did.