Many cities in China are now experiencing the booming period of metro construction. A critical and urgent problem is how to work out a sound network planning for the metro system before the concrete line implementation. Based on the experiences of metro network planning in China these years, the paper intends to explore some critical issues in this field. That includes the reasoning of the rational scale of the metro system, the spacial form and framework planning and the integration of the metro system with other public transport systems in the city.