Optical frequency standard laboratory’s main task is establishing and maintaining optical frequency standards since 1960s. In 2005, the iodine stabilized 532 nm Nd:YAG laser system achieved a stability of 5E-15 at 100s of averaging time, which won the second prize of the National Science and Technology Progress. In 2007 the strontium optical lattice clock project started. In 2015 the first evaluation and absolute frequency measurement results were reported to the frequency standard working group of CCTF, which are accepted and regarded as one of the source data to calculate the international recommended value of strontium clock. Recently, an ultra-stable clock laser with a stability of 3E-16 was built, and the time-interleaved self - comparison showed a measurement stability enters E-18 level after 40000s of averaging time. The second strontium clock is being built at NIM’s Changping Campus.