Lotus histidine kinase 1 is a cytokinin receptor protein which serves an important function in symbiotic signaling pathway and nodules formation.Two sets of eukaryotic expression vectors were built and expressed in tobacco expression system and baculovirus insect expression system to study the function of LHK1 protein.The results showed that it can be expressed in tobacco and insect cells.The LHK1 protein expressed has histidine protein kinase activity in vitro.It will be useful for further studying the biochemical mechanism of LHK1 in symbiotic signaling pathway.