The SHRIMP UPb dating of the gneiss in the Tongmai region shows that: ① the mean UPb age (42Ma) for the metamorphic zircon and the younger crust of metamorphic compound zircon is in MidEocene epoch, which is consistent with the peak age of the continentalcontinental collision. The starting time of the IndiaEurasia collision should be little earlier than 42Ma. ② The oldest age for the older core of the compound metamorphic zircon(inherited zircon) is about 201Ma, equivalent to early Jurassic, indicating that the age of the sedimentary protolithic of the gneiss in the Tongmai region should be later than Triassic. ③ The genesis and types of the zircon and their significance, the age of the gneiss, and the collision time of the IndiaEurasia continents are discussed in the paper.