In this study, miR166a with differential expression was candidated from the small RNA libraries of the halophyte Halostachys caspica roots established under high salinity (600 mmol·L^-1 NaCl), some work was carried out as follows. miR166atargeted gene was predicted from this species transcriptome by bioinformatic analysis; the miR166atargeting was identified with the technology of 5′ RLMRACE; miR166a precursor and full length of ATHB8like were obtained by PCR and RACE methods and fully analyzed by bioinformatic softwares. The results showed that predicted target was ATHB8like; 5′ RLMRACE validated the accurate cleavage site of the target by H. caspica miR166a between 14^th to 15^th base of its mature miRNA; H. caspica mature miR166a was highly conserved compared to different plant species; the miR166a precursor could be folded into complete hairpin structure and was met with various indexes of miRNA precursor and did not reflect the conservation in evolution by aligning with plant species available; the full length cDNA of ATHB8like is 2 786 bp that open reading frame is 2 526 bp with putative 841 amino acids containing a HDZIP III domain and H. caspica ATHB8like was conserved compared to those ATHB8 of different plants. This work will lay the foundation for further studying biological functions of H. caspica miR166a and its target.