The main production areas of coix seed (Job's tears) are distributed mainly in Guizhou, Yunnan, Fujian and other places.

Coix seed is the mature seed kernel of Coix lacryma-jobi, a plant in the grass family. It is both a common cereal ingredient and a traditional material used as both food and medicine. The so-called production areas of coix seed refer to regions where Coix is grown in concentration and harvested and processed on a relatively large scale; the conditions of the production area directly affect the plumpness and taste of the grains.

Domestic Coix cultivation is mostly concentrated in warm and humid regions, and it is distributed in Guizhou, Yunnan, Guangxi, Fujian and other places. Among them, the Xingren area of Guizhou has a relatively large planting scale and has long enjoyed the reputation of China's hometown of coix. Coix from some mountainous areas of Fujian is also known for its long cultivation history and stable quality, while Taiwan and other places have scattered plantings as well.

Coix prefers warm and humid environments and is mostly planted on sloping land or paddy fields at moderate altitude with convenient drainage and irrigation. When the production area has ample sunshine and suitable day-night temperature differences, the grains are more likely to fill out well. After harvest, the seeds still need to go through processes such as hulling and fine selection before they become the coix seed sold on the market. Coix seed from different production areas differs slightly in grain size, color and starch content.

In addition to domestic cultivation, some coix seed on the market comes from Southeast Asian countries such as Thailand and Vietnam. When purchasing, pay attention to the origin label on the packaging, observe whether the grains are plump and the color natural, check whether there is any off odor, and judge the storage condition together with the degree of dryness, so as to select a better-quality product.