Abstract: Natural gas storages become more and more important in China with an increasing consumption of natural gas. Aquifer traps and depleted oil and gas pools are main types of underground natural gas storages in the world. However, in China, petroleum provinces are generally far from big cities and petroleum is mostly often produced from lacustrine deposit which is highly inhomogeneous, limiting the potential of storage capacities. Therefore, we suggest that aquifer traps of Paleozoic marine deposit should be explored as the main type of underground storages of natural gas in China. In this paper, gas engineering methods are introduced to formulate a method of quantified optimization selection of aquifer traps as underground natural gas storages. The parameters, like peak demand of natural gas, aquifers' permeability, bury depth, volume of traps, drilling and compressor power cost, and a group of combined equations related to these parameters are established. The resolution of these combined equations leads to an optimization of investment for each trap. By comparing the discounted investments and pay-off of all the traps, one trap could be selected as the favorite to be constructed as underground natural gas storage. The gas engineering methods make the optimization selection of aquifer traps based on quantified evaluation, which will provide technical support for constructing aquifer traps in China.