  We report the absolute frequency measurement of the 5s2 1S0-5s5p 3P0
transition in 87Sr optical lattice clock (Sr1) at National Time Service Center
(NTSC). Its systematic frequency shifts are evaluated carefully with a total
relative uncertainty of 5.1E10-17. The measured absolute frequency is 429 228
004 229 872.91(18) Hz with a relative uncertainty of 4.13E10-16, with reference
to the ensemble of primary and secondary frequency standards published in the
Circular T bulletin by BIPM through a global navigation satellite system (GNSS)
link.
