Timing of the collision between India and Eurasian plate is still debated. In this paper, zircon U-Pb geochronology, whole rock geochemistry and zircon Hf isotope analysis have been carried out for the Tuolong intrusion exposed in the middle of Linzhou County, Tibet, in order to further constrain the collision time of the India-Eurasian plate. The quartz monzonite porphyry outcropped in Tuolong pluton intruded into the Pana Formation as stock. Zircon U-Pb dating results show that the quartz monzonite porphyry was formed in Eocene (50.5±0.6 Ma) with εHf (t) value of -0.6 to -0.5. Quartz monzonite porphyries display metaluminous and shoshonitic characteristics with low A/CNK and high K₂O/Na₂O value and high K₂O contents. They are generally depleted in high field strength elements (Nb, Ta, Ti and P) and enriched in large ion lithophile elements (Th, U and Pb). Chondrite- normalized REE patterns are characterized by high (La/Yb)_N values (15.3~16.3) with weak negative Eu anomalies(0.56~0.69), the differentiation of light and heavy rare earth elements is obvious. The low A/CNK value, the negative correlation between P₂O₅ and SiO₂, and the positive correlation between Y content and Rb content indicate that the quartz monzonite porphyry is I-type granite. Combined with results of previous studies, it is considered that the Tuolong quartz monzonite porphyry may be the product of partial melting of the relatively ancient metamorphic intermediate-basic rock, and was formed as the consequences of subduction and break-off caused by the India-Eurasian plate collision, indicating that the India-Asia continent collision should have occurred before 50 Ma.