The Kalu’an lithium deposit is located in the Altay orogenic belt in northern Xinjiang,which is a hard rock type lithium deposit with spodumene as the main mineral. A lot of research on the petrology,mineralogy,petrochemistry,age and petrogenesis in the Kalu’an lithium deposit,but few reports have been made on the Characteristics of ore-forming fluids.Methods: This paper reports He and Ar isotopic compositions of spodumene and quartz fluid inclusions in Kalu’an lithium ore.Results: The analytical results indicate that the n(3He)/n(4He) ratio of spodumene-bearing pegmatites is 0.25 ~ 3.19 Ra(average 0.97 Ra);and that of spodumene—barren pegmatites and outer pegmatites is 0.13 ~ 8.86 Ra (average 3.10 Ra),which is between crust and mantle derived He.According to the crust mantle binary mixing model of ore-forming fluid,the proportion of mantle fluid in spodumene-bearing pegmatites is 3.55% ~ 48.92%,with an average of 14.67%;the proportion of mantle fluid in spodumene—barren pegmatites and outer pegmatites is 1.70% ~ 81.79%, with an average of 17.13%. The n(40Ar)/n( 36Ar) of ore-forming fluid of spodumene-bearing pegmatites ranges from 552.5 to 13353.0,n(40Ar*)values range from 46.52% to 97.79%,with an average of 87.25%, and the Ar contribution of atmosphere is 12. 75%.Conclusions: The results show that the ore-forming fluids are mainly crust derived fluids,and some mantle derived fluids is mixed with reformed saturated atmospheric water.With the progress of mineralization,mantle He and atmospheric saturated water reformed Ar decreases.It is worth noting that the mantle-derived fluid in the ore-forming fluid of the Kalu’an lithium deposit does not really come from the mantle material invasion,but is more likely to come from the immature continental crust of the Proterozoic.The Kalu’an lithium deposit in Xinjiang was formed into the post-collisional orogenic stage in the late period of continental collisional orogeny.The extension of the late period of orogeny led to decompression melting of the old crust and the young crust containing mantle-derived material, and the magmatic fluid formed by the melting was subsequently transformed by meteoric precipitation to form the present ore-forming fluid.