Strontium optical lattice clock plays a key role in fundamental physics research and precision measurement of time and frequency. Based on the research of its first strontium optical clock, NIM-Sr1, the National Institute of Metrology(NIM) has conducted in-depth study to enhance the performance of its optical clocks, designed and built the second strontium optical lattice clock, NIM-Sr2. Benefited from the experiences gained in the quantum reference preparation, clock transition interrogation and systematic frequency shift evaluation of NIM-Sr1, the physics apparatus of NIM-Sr2 is redesigned and improved. A vacuum differential pumping stage is added between the atomic oven and the magneto-optical trap (MOT) chamber, which reduces the MOT chamber pressure variation to 1×10 -8 Pa when the oven is switched between on and off. By replacing the coils in Zeeman slower with permanent magnets, optimizing the winding of the water-cooled anti-Helmholtz coils, and extending the viewport for Zeeman slowing laser beam, the inhomogeneity of the ambient temperature in the MOT region is reduced to 0. 166 K. The frequency evaluation revealed that these improvements significantly reduced the systematic shift uncertainty of NIM-Sr2 to 7. 2×10 -18 .