The field and indoor results show that the gneissic alkali granite from Lanshantou was converted from paleozoic sedimentary rock. Its chemical composition presents high Si( SiO2 = 75%- 77%),alkali-rich(Na20+K20 = 8.38% - 8.60%),1ow AI(A1203 = 11.72% - 12.05% ) ,and poor in Ca( CaO = 0.09% - 0.53% ). It was rich in the large-ion lithophile elements such as Rb,Ba,Th, U,Pb and poor in the high field strength elements such as Nb, Ta,Zr, Hf and Ti. The gneissie alkali granite presents relatively high LREE ( LREE/HREE = 6.32 - 9.86 ) elements and obviously Eu (SEu = 0.42 - 0.64 ) negative abnormality. Based on the base of studying the zircons CL images,The age of mantle of zircon with three-tier structure (core, mantle, shell ) is 245 Ma or 235 Ma which reflects the first ultra-high pressure metamorphic time and also is the time of forming of the gneissie alkali granite and equivalent to the Early-Middle Triassic. The age of new shell of metamorphic composite zircon is 222 - 198 Ma which reflected the second metamorphic time and equivalent to Late Triassic. The U-Pb dating results of old nuclear of metamorphic composite zircon reveal that the ages of magmatic and detrital zircons have both proterozoic era (864 Ma -781 Ma - 701 Ma -688 Ma - 631 Ma-598 Ma -592 Ma)and paleozoic era(544 Ma-500 Ma-447 bla -339 Ma- 306 Ma). In summary, the ear of protolith of host rock can not be proterozoic and may be palaeozoic.