Chang-hwa county is situated in central Taiwan . Da-tu river is in north as the boundary between Chang-hwa and Taichung , while Zhou-shui river is in south to divide Chang-hwa and Yuan-lin county. Chang-hwa neighbors with Nan-tou county with Pa-gua mountain in its eastside, while Taiwan straits is in the west of Chang-hwa. The measure of area is 1,074 square kilometers, with a total population around 1.31 million. The density of population per square kilometer reaches 1,225 persons.

There are 8,949 factories in Chang-hwa, the density of factory per square kilometer is 8. The economy type in Chang-hwa is mixing agriculture with industry. Nine developed industrial areas or scheduled industrial lands include Chang-ping, Chung-hsin, Fu-hsin, Fang-yuan, Bei-tou, Bei-dou, Dai-hsin industrial district, Niu-chou chi, and Tien Chung Yang industrial land. In addition to Chang-pin industrial district that is assigned and scheduled in Economic Yuan's development policy, the rest has been planned and scheduled by local government that is based on industrial lands mode to be developed. Most registered factories produce metal products, textile goods, and plastic products. There are 375,497 automobiles and 778, 916 motors that are registered in Chang-hwa, the density of automobiles per square kilometer is 942.

There are three air quality automatic monitoring stations set in the territory of Chang-hwa, they are located in Chung-shan elementary school (Chang-hwa station), Xian-xi high school (Xian-xi station), and Wan-ho elementary school (Er-lin station). The average pollution standards index monitored in Chang-hwa county from 1996 to 2003 is 59. Averagely, the days with fine air quality to normal in a year are 96.54%, the bad air quality are only 3.46%. The major pollutant includes suspension particles and ozone.

There are four major river basins in Chang-hwa county, including Zhou-shui river, Yuan-lin drainage trench, Fang-ya trench, and Yang Zi Chu river.