Janus 2D materials have drawn substantial attention recently owing to its extraordinary interface properties and promising applications in optoelectronic devices. However, the scalable fabrication of high‐quality Janus 2D materials is still one of the main obstacles to hinder its implementation in the industry. Herein, a new method (called “chemical breakdown”) is developed to obtain large‐area uniform Janus graphene oxide (J‐GO) films with high‐quality. Moreover, the first application of J‐GO in the field of memristive devices is presented for neuromorphic computing. In particular, crossbar arrays of Ag/J‐GO/Au memristive devices that exhibit threshold resistive switching (RS) with enhanced performance are fabricated, e.g., low leakage current (≈10−12 A), low operation voltage (≈0.3 V), high endurance (>12,000 cycles), and electro‐synaptic plasticity. This work provides a novel strategy to obtain large‐area, continuous and uniform Janus 2D films, and proposes a new application for Janus 2D materials in a hot topic (i.e., neuromorphic computing) within the field of solid‐state microelectronics.