Abstract: The ophiolites along the Yarlung Zangbo suture zone outcroped in 3 types，large maficultramafic body，stratified cumulative，diabasic dike and sheet swarm，and deep sea sedimentary formation in the Gangrenboqi and Bailang regions. The opniolitic complex constrict rapidly in the Renbu region，only pearlchain shaped stocks extend eastwarded then disappeared. There is the lack of ophiolite in Lhasa region，but a set of intermediate to acid volcanic sediments out cropped in the relevant position of the ophiolite corresponding in the western. We carried out the geological tectonosedimentary investigations in locations of such 3 types. The preliminary data show that the original emplacement structures exist in both Bailang and Renbu ophiolite outcropts. A tectonic window inside of the Bailang ophilite body is identified，and the parallel even conformable contact relationship can be observed locally between ophiolite bodies and flysch layers on both side of the zone. The country flysch layers kept low angle even parallel with the stocks surfaces in Renbu region with their thermal optalic metamorphic structures. All rocks underwent low greenschist metamorphism and were then fractured without regional tectonic polarity，and no any large shear zone in northsouth direction exists between country layers and mafic rock bodies. The geologic information show that the whole system is in situ，but not foreign resulted from subduction nor collision of the plates. The Mesozoic sedimentary facies and lithology are similarin both north and south segments of the Lhasa profile，and its sedimentary evolutionare corresponding in time. These recorded a history of the evolution of the intact basin. All geologic information above does not warrant a postulate that the Yarlung Zangbo ophiolite zone represents the relic crust of a great ocean thousands km in width，the Neotethys should be in fact backarc basin collapse with its juvenile narrow oceanic crust.