Abstract: Heat shock protein (HSP) 70, as a molecular chaperone and extensively studied protein in environmental toxicology, plays a key role in membrane translocation, protein degradation, and regulatory process. However, as toxicology and risk assessment of freshwater, characterizations of HSP70 in rare minnow, Gobiocypris rarus, remain unknown. In this paper, we described the full-length cDNA of HSP70, designated as GrHSP70, by cloning through rapid-amplification of cDNA ends (RACE) technique from the liver of Gobiocypris rarus for the first time. The GrHSP70 shares high nucleotide sequence homolog, corresponding to amino acid sequence homology (>95%) with other fish species by NCBI blast analysis. Through quantitative real-time PCR (RT-PCR), we obtained the distribution of GrHSP70 in thirteen tissues of the untreated Gobio-cypris rarus juveniles and its expression profile in liver after pentachlorophenol (PCP) exposure. The re-sults indicated that mRNA transcription level of GrHSP70 is tissue-dependent, with the highest expression in the gonad tissue. Moreover, GrHSP70 is significantly up-regulated in liver by a concentration/time-depen-dent manner after PCP exposure. In summary, our results suggest that GrHSP70 may serve as a very sensi-tive biomarker for a toxicology and risk assessment of freshwater pollution in China.