Homology cloning combined with RACE techniques was applied to clone the cDNA of heat shock protein 70 gene (hsp70) from Chrysanthemum nankingens and real–time quantitative PCR (qRT–PCR) was conducted to analyze the expression patterns of this gene under 40 ℃ for 0 h, 0.5 h, 1 h, 2 h, 3 h and 6 h. The results showed that the full cDNA sequence cloned is 2 224 bp, which is determined to be hsp70 gene of Chrysanthemum nankingens, and subsequently named Cnhsp70 as it shares 88% homology with Saussurea medusa at nucleotide level and 98% homology with Ageratina adenophora at amino acid level. Cnhsp70 contains a 1 944 bp open reading flame (ORF), which encodes 647 amino acids containing the HSP70 family sequence tags with a predicted molecular mass of 70 900. Real–time quantitative PCR presented that the expression of Cnhsp70 was up-regulated quickly in a short time after heat stress and get to the highest level 3 h after stress, which was rapidly down-regulated 6 h after stress.