Abstract: Some technological improvements were carried out in physics package for rubidium atomic frequency standard. The structure optimization of magnetron microwave cavity improved the signal to noise ratio. The optical path was optimized, and the signal intensity on the photo detector increased by 25%. Besides, a model of magnetron microwave cavity was established using Ansoft HFSS software. The field distribution and resonance frequency were simulated. The numerical simulation and performance test indicate that the modified magnetron cavity operates at TE₀₁₁ mode and has a high quality factor. A preliminary test on the modified rubidium atomic frequency standard was carried out, and the high performance of physics package was validated by achieved an excellent short-term stability as low as 6.0×10^-13τ^-1/2(τ is sampling time). The achieved experimental results show that the modified magnetron microwave cavity can meet the requirement for rubidium atomic frequency standard, and is suitable for application in high performance space rubidium atomic frequency standard.