Objective To synthesize N-stearyl tyrosine disodium (NST-2Na) and dipotassium (NST-2K) and to determine their critical micelle concentration (CMC). Methods N-stearyl tyrosine (NST) was synthesized from stearic acid via two step reactions and then basified by NaOH or KOH to obtain the target compounds. The feasibility of UV spectrophotometry for measuring the CMC was determined by the CMC trial of sodium dodecyl sulfate (SDS) and N,N-diethyl aniline (DEA) was used as the probe. The CMC of two NST salts was measured by the UV spectrophotometry. Results The results of high performance liquid chromatography (HPLC) showed that the purity of NST-2Na and NST-2K was 98.35% and 92.65%, respectively. The CMC values of SDS determined by the UV spectrophotometry were consistent with those of literatures. The CMC was 27.5 mg/100 mL for NST-2Na and 25.0 mg/100 mL for NST-2K. Conclusion The UV spectrophotometry is a simple and reliable method for measuring the CMC of NST salts.