Paleozoic granitic magmatism is well developed in Nalati area of West Tianshan Mountains. Based on field work, petrographic studies and LA-ICPMS zircon dating, the authors divided granitic magmatism in Nalati area into two stages. The first stage is from Late-Ordovician to Late_Devonian, and the granitoids formed in this stage have experienced a strong deformation and developed gneissic schistosity and large exposed areas of diorite, quartz diorite, granodiorite and monzogranite intrusions. From west to east, they include Senmutasi intrusion, Haerwenke intrusion, Kekesuhe intrusion and Nalati intrusion. Granitoids of this kind in the study area were mainly formed between 485 Ma and 366 Ma and constitute the main body of the granitoids in Nalati. The second stage is Carboniferous and the granitoids formed in this stage are located in the north of the first stage granitoids or intruded into the first stage granitoids, and their exposed area is usually small. They have only undergone a weak or no deformation. Along the NEE-trending Nalati tectonic belt, there exists the feature that the formation ages of the granitoids gradually become younger from west to east, and become younger from south to north across the Nalati tectonic belt. Zircon Hf isotope studies reveal that the granitoids formed between Late-Ordovician and Late-Devonian in this area have three kinds of sources. The first (t2DM=1200～1600 Ma) is Mesoproterozoic crust, the second (t2DM =700～1600 Ma) is Meso- and Neo-Proterozoic crust, and the third (the values of t2DM are similar to or a little older than the formation ages of the granitoids) is a juvenile crust. Carboniferous granitoids also have three kinds of sources. The first (t2DM =1000～1700 Ma) is a Meso and Neo-Proterozoic mixed source, the second (t2DM≈400 Ma) is an Early Paleozoic juvenile crust, and the third is a mixed region of Early-Carboniferous depleted mantle and ancient crust. Zircon Hf isotope researches on granitoids suggest that there exits a Meso- and Neo-Proterozoic crustal growth event in Nalati area. The Paleoproterozoic basement considered by present researchers may include Neoproterozoic, Mesoproterozoic, Paleoproterozoic and Archean materials, and its internal structure is so complex that we should do much future work on it. Chronological framework and deformation characteristics of granitoids suggest that the Late Devonian period may represent the end of the Paleozoic ocean-continent transition in the Tianshan Mountains. Zircon Hf isotope studies suggest that there were two events of mantle material addition that took place in Early Silurian and Early Carboniferous respectively. The former was a period of the Tianshan Paleozoic ocean subduction, and during this time the granitoids were formed by partial melting of a juvenile crust with the addition of some mantle materials. The latter represented a crustal growth event in Early Carboniferous, which suggests an influx of some mantle materials in a strong continental extension stage after a collisional orogeny.