Crab grows by periodic molting, which is controlled by molt-inhibiting hormone (MIH) and ecdysteroids. Untranslated regions (UTRs) play crucial roles in the posttranscriptional regulation of gene expression. In this study, using crab collected from Changjiang (Yangtze), Huanghe (Yellow), Liaohe, and Yalujiang rivers, 33 haplotypes of the 3ꞌ-UTR of ecdysteroid-regulated protein (ERP) gene were identified, of which 14 haplotypes were observed in more than one individual. One hundred and forty clones of haplotype h2 (41.5%) were observed in samples from all the 4 rivers. Three haplotypes were observed to be insertions. For the whole crab sample, we found a positive Tajima’s D value and a negative Fu’s Fs test (Tajima’s D value = 0.98726; Fu’s Fs test = -27.382), although the P values were not significant (P > 0.10). The network profile of these 33 haplotypes presented a single core pattern with h2 as the core. In this study, we found that the UTR of ERP gene had a considerably high genetic polymorphism among crab from regions south to north of China. Furthermore, we observed a relatively high genetic divergence among different haplotypes, which would suggest a high diversity of the crab gene pool.