Abstract: Under the background of urbanization and industrialization, many Agricultural Heritage Systems (AHS) sites in mountainous areas still maintain traditional small-scale agriculture (TSA) that relies on human labor due to the difficulty in using modern machinery. TSA has been widely regarded as a relatively small industry owing to a low annual income. TSA in AHS sites usually has a history of over thousands of years and is important for maintaining a living for local households. Why are there still a large number of farmers engaged in agriculture in AHS sites? From an economic perspective, this paper selected the China Nationally Important Agricultural Heritage Systems (China-NIAHS), Kuancheng Traditional Chestnut Cultivation System in Hebei Province, as an example, taking the chestnut farming household as a basic unit, to examine its sustainability. Data were collected by using the random questionnaire method. The survey information included the direct material inputs, labor inputs, outputs of chestnut farming, and the migrant workers' workplace information, duration and income. The labor consumption of chestnut farming and migrant work were accurately calculated. The labor input-return (LIR) model was constructed to calculate the LIR rate of chestnut farming and migrant work in each chestnut farming household. A comparative analysis was carried out to identify differences. Results showed that chestnut farming households usually had a small farmland area (about 0.57 hectare per household) and most maintained traditional production methods. Only a few households used fertilizers and pesticides to farm chestnut trees. An average household spent 121.4 laborsxdays in cultivating chestnuts due to extensive management. An average chestnut farming household had 2 migrant workers and each spent 8.9 months per year doing migrant work. Each chestnut farming household thus expended 537 labors×days for migrant work. The labor input of migrant work was 4.4 times that of chestnut farming. Likewise, a chestnut farming household often had an annual income of 15 623.3 Yuan RMB from chestnut farming due to the relatively high price of chestnut, and could get an annual income of 59 243.7 Yuan RMB from non-farm jobs due to the low degree of peasant culture, skills shortage, and low monthly income. However, the results showed that TSA had a higher LIR rate (1.2 times) than migrant work. This is contrary to the common impression that TSA is a low benefit system. This also explains why most farmers are unwilling to give up chestnut planting from an economic perspective. Chestnut farming does not require a lot of labor input and each chestnut farming household has surplus laborers to perform migrant work, so they can adapt to the social and economic transformation.