Abstract: 【Objective】 Many Paeonia plants have poor fecundity. Paeonia ostii ‘Feng Dan’is a shrub that originated from Anhui Province and now planted widely in Hunan, Chongqing, Shandong, Sichuan and Henan in China. P. ostii seed contains abundant monounsaturated fatty acid, including α-linolenic acid(ALA), an essential fatty acid that humans cannot synthesize. Thus, the seed of P. ostii is an excellent raw material for the production of a new type of edible oil. Compared with the low fruit set of other Paeonia plants, the fruit set of P. ostii is high, which provides the possibility for large-scale production of its seed. The seed set of P. ostii from cross-pollination is significantly higher than that from self-pollination, which means that seed production is outcross pollinated and pollinator dependent. Thus, the foraging behavior of the main P. ostii pollinators is still unclear, which is important for gaining higher yield and seed quality. 【Method】 We investigated the pollination behavior of the major pollinators of P. ostii in Dianjing, Northeastern Chongqing, China in March and April from 2015 to 2017. Through fixed-point observations, we examined the visiting frequency, residence time, and rate of stigma contact of major pollinators. Through tracking observation, we measured the flying distance of main pollinators between two consecutive visits using a portable infrared rangefinder(Shendawei SW-A/B, Dongguan, China). Occasionally, honeybees flew away and returned to revisit the same flower, which was regarded as a single visit. Through field collections and laboratory observations under a microscope, we observed the pollen load of the main pollinators by netting the forager from the visited flower, and then transferring them to a poison flask and taking to the laboratory. All pollen grains on the poison flask and on the surface of the pollinator body were flushed with 50% alcohol and transferred onto a glass slide before being observed and counted under a microscope. The source of pollen grains was not identified; in our preliminary observation, all pollen grains carried by bees were found to be from P. ostii under a scanning electron microscope. To confirm pollen deposition by the main pollinators on the stigma after a single visit, the unopen flower was bagged until opening. The petals of the large flower were taped to form a half closure after fully opening, which allowed the pollinator to contact the stigma before collecting pollen grains. When the stigma was visited by a pollinator, it was transferred into a centrifuge tube and brought into the laboratory to observe and count under microscope.