An expanse of fairly level and treeless terrain is known as a plain. More than half of the land in Taoyuan Hsien is plains, and is divided into Taoyuan plain, Linkou plain, and Fukou plain. Taoyuan plain is the largest.

The Linkou plain and Fukou plain are 300 meters and 250 meters above sea level. The plains were soil deposits created by rivers flowing out of mountains in early times. Then the earth's crust raised slowly and became what it is now. If you dig in the earth, you will find a thick level of red soil and a pebble layer. The pebble layer is evidence that the plain was created by rivers a long time ago.

The altitude of Linkou plain and Fukou plain are higher. Their surfaces are steeper due to the erosion of the peripheries of the plain. A number of golf courses were built on these two plains in the last few years. The latitude of Taoyuan plain is lower. This plain is flat due to less erosion.

Taoyuan plain is the most important rice producing area in northern Taiwan. A number of ponds were built in the early stages for water storage and irrigation. These ponds are distinctive features on the Taoyuan plain. In the last two decades, a number of projects that required a large amount of land were constructed on the Taoyuan plain, such as CKS airport, Guan-yin industrial zone, and Da-yen industrial zone.