Abstract It is significant to know the nesting and foraging behavior of wild bee-pollinator, Megachile maritima, which is one of the important pollinators in Mu Us sandland, for protecting its habitat. 【Methods】The whole nesting process of M. maritime was observed by visual observation and photographing; visiting frequency and duration of each visit on nectar plants were counted using stopwatch in 2 m × 2 m plots, and daily activities of M. maritime were observed in 2 m× 2 m plots incessantly from 7: 30 to 18: 30 for 7 days. 【Results】 M. maritime excavated nest in sand, with one cell per nest. At first, female of the bee searched for the nesting site, excavated nest burrow, and then constructed and provisioned cell, and finally oviposited and closed the cell. About 9 hours were needed for nesting one cell; 26-29 pieces of leaves were needed for constructing one cell. The bee executed 11-12 pollen and nectar trips for each cell. A single egg was laid on the surface of the provision. The frequencies on Hedysarum laeve and Leonurus sibiricus were 13.23±6.49 flowers per minute and 16.72±4.84 flowers per minute, respectively; and the duration of each visit on the two plants were (3.08±2.48)s and (2.49±1.31)s, respectively. M. maritima bees were more active during 12:00-14:00 on sunny days. 【Conclusions】 Nesting behavior of different individuals of M. maritima was very similar. There was a significant difference in visiting process, visiting frequency and duration of each visit on the two nectar plants.