Objective To investigate the effect of acetylcholine characteristic ultra-low frequency transcranial magnetic stimulation (ACh-TMS) on spatial learning and memory function in rats with Alzheimer's disease (AD) and possible mechanisms.Methods Sprague-Dawley rats were randomly divided into normal (N) group,model (M) group,sham-operation group (P group),sham-stimulation group (M+P group),ACh-TMS group,and donepezil group,with 10 rats in each group.A rat model of AD was established by injection of Aβ_1-42 at the bilateral hippocampus.The Morris water maze test was used to evaluate the spatial learning and memory function of all rats.The levels of brain-derived neurotrophic factor (BDNF) and acetylcholine (ACh) were measured,as well as the changes in the activities of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) in the hippocampus.The modified Highman Congo red staining was used to observe the deposition of amyloid substances in the hippocampus.Results Compared with the M+P group,the ACh-TMS group had a significantly shorter mean escape latency and significant increases in the swimming time percentage in target quadrant and number of platform crossings (P<0.05),as well as significant increases in the content of BDNF and ACh and the activity of ChAT (P<0.05).All groups except the N and P groups showed the deposition of amyloid substances in the hippocampus.Conclusions ACh-TMS may improve the spatial learning and memory function of AD rats,possibly by increasing the content of cholinergic transmitters in the central nervous system and upregulating the expression of BDNF in the hippocampus.