Artificial synaptic devices are the basic composition units for neuromorphic computing processors that realize massive parallel computing. However, the n-type organic transistors have failed to achieve good performance as an artificial synaptic device for neuromorphic computing until now. Here, a vertical three-terminal n-type organic artificial synapse (TNOAS) using a lithium ion-based organic dielectric and the n-type donor-acceptor (D-A) conjugated polymer-naphthalene-1,4,5,8-tetracarboxylic-diimide-thiophene-vinyl-thiophene (NDI-gTVT) as the channel is proposed. The TNOAS achieves nonvolatile conductance modulation with high current density operation (≈10 KA cm −2 ) at low voltage and mimics the basic functions of biological synapses, such as long-term synaptic plasticity and paired-pulse facilitation. The minimum energy consumption of a response event triggered by a single action potential is 6.16 pJ, which can be comparable with p-type counterparts. Moreover, simulation using handwritten digital datasets exhibit a high recognition accuracy of 94%.