This paper presents a wireless opto-electro neural interface system that combines ECoG recording and optogenetic stimulation for closed-loop neuromodulation on small freely behaving animals, such as rodents. The prototype opto-electro neural interface array includes 4 μLEDs for optical stimulation and 2 microelectrodes for ECoG recording, all on a flexible polyimide substrate. The detachable headstage, connected to a custom-designed USB dongle via Bluetooth low energy (BLE), is capable of wirelessly receiving user commands to selectively drive the μLEDs, and transmitting the recorded ECoG data, to enable bidirectional data communication. A proof-of-concept in vivo experiment was conducted on a freely behaving rat, while successfully applying optical stimulation to synchronize the wirelessly recorded ECoG signals.