Placement is a critical step in layout automation for analog and mixed-signal (AMS)-integrated circuits (ICs). It determines the proximity of devices and influences the wiring topology, significantly impacting post-routing parasitics and coupling capacitance. Existing analog placement techniques mainly focus on geometric constraints in analog building blocks. However, there yet lacks an effective way to consider the system-level signal flow for sensitive AMS circuits. Leveraging prior knowledge from schematics, we propose considering the critical signal paths in automatic AMS placement. A multilevel analog layout automation flow is further developed to reduce manual efforts in synthesizing hierarchical AMS circuits. Experimental results demonstrate the efficiency and effectiveness of our proposed framework with a 22.8% reduction in routed wirelength compared to state-of-the-art AMS placer and a 10-dB improvement in the signal-to-noise-and-distortion ratio (SNDR) for an ADC.