The program is scheduled for August 7, 2015 to January 5, 2017. The aim of this program was to investigate the source and releasing mechanisms of arsenic in groundwater, and survey of arsenic accumulation in farmland soil by summarized the researches of hydrological and geological properties of the Pingtung Plain, survey data of groundwater qualities from Environmental Protection Agency, Environmental Protection Bureau of Pingtung county and Water Resources Agency, sampled groundwater from 29 monitoring wells and 18 pump-wells, 29 soil profiles and soils in 10 areas. According to the results, the concentration of arsenic was higher than 0.01 mg/L in 20 wells, was higher than 0.05 mg/L in 8 wells, and arsenic in groundwater in pump-wells is generally higher than that of monitoring wells, it’s related to well-depth and the redox condition in groundwater. The speciation of arsenic in groundwater is mainly inorganic phase, and the contents of As (Ⅲ) and As (Ⅴ) are mainly from groundwater of pump-well and groundwater of monitoring wells. It is speculated that the release of arsenic is caused by the reduction of groundwater, due to the concentration of arsenic, iron and nitrogen containing compounds changes. Survey results showed that the arsenic content in Kanding Farmland soils was higher than the regulatory standard, the main reason cited for the irrigation groundwater. It’s showed that arsenic is held together with hydrous oxides od Fe and Al, and released by reduction in aquifer by core-drilling. Compared to the core samples from Central Geological SURVEY, MOEA, the results showed arsenic enriched in a particular phenomenon in the formation of the depth. The simulated arsenic concentration of groundwater in Pingtung area shows that the arsenic concentration of groundwater in the coastal area mostly exceeds the drinking water standard, and the inland area is almost below the drinking water standard. The arsenic content of soil showed the same distribution. The health risk assessment of arsenic exposure at the site of arsenic contaminated sites is known as the median value of the risk of quotient and carcinogenic risk, which exceeds the acceptable risk, and if the person is eating the site Rice, will have a higher risk of cancer.