Exposed in the northern Beidashan area of Alxa, minor Precambrian rocks have been traditionally considered to be a part of the Longshoushan Group. The age and isotopic characteristics of these Precambrian rocks are important for the understanding of the local basement characteristics and the tectonic architecture of north Alxa area. This study presents detailed petrology, zircon U-Pb age and Hf isotope of the Haisen Chulu gneiss from the north Beidashan area and discusses its tectonic implications. Field observation and petrological features indicate that the Haisen Chulu gneiss is orthogneiss. LA-ICPMS zircon U-Pb dating performed on the inner part of the zircons yielded an upper intercept age of 1 408±29 Ma (MSWD=13) on the concordia diagram, which indicates that the protolith for the gneiss intruded at~1.4 Ga. The zircons from Haisen Chulu gneiss show positive εHf(t) values between -4.38 and +6.68, and the two-stage Hf model ages are in the range of 2 091 to 1 624 Ma, indicating that the protoliths were mainly derived from the juvenile crust. This study, in combination with previous work, indicates that the Precambrian rocks outcropped in northern Longshoushan-Beidashan area were formed in Mesoproterozoic or later instead of in Archean or Paleoproterozoic as previously proposed. The northern Longshoushan-Beidashan area could not be part of the Alxa block during early Precambrian time.