We present a methodology about real-time 3D fluid simulation system using BCI (brain–computer interface). Spectators appreciate our work with their emotion. The advance of technology has exerted huge impacts on arts and as result a new genre called digital art has emerged. In digital art, interaction is an important element. Various types of interaction are bein g implemented in digital art using touch, hand gesture, sound, movement, etc., even brain wave. Usually, digital artists pursue interactions in their art work; the reason is that they want spectators’ deep appreciation and involvement. However, many of interactive digital art works fail to induce interaction as much as the artists expected. If visible interaction is weak, or interaction result is weak, spectators are not immersed much in the work. Nowadays, there are many interactive digital arts. In digital art, new type of interaction is needed to captivate spectators. So, we tried to implement BCI interaction digital art prototype (tentative title: Soul flow). Electroencephalography (EEG) is the recording of brain electrical activity along the scalp. We measured user’s EEG signal using MindSet (the MindSet senses EEG brainwave data to power the innovation of laboratory researchers and application developers like no other EEG device in the world. It delivers RAW signal, power frequency bands and NeuroSky eSense meters:attention, meditation. http://www.neurosky.com/products/mindset.aspx) to take user’s emotional state on appreciating digital art. We can get user’s emotional state in four categories (attention/inattention, meditation/uneasiness) and these emotional states interact with 3D fluid simulation system in real-time. In this art work prototype, each spectator experiences each different fluid (scale, speed and visual) because each spectator has different emotional state. Our art work prototype expressed the flow through water flow simulation. Flow means the mental state of operation in which a person performing an activity is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity. In essence, flow is characterized by complete absorption in what one does (The psychology of optimal experience 1990). In addition, it means stream in water flow. We pursued these concepts and expressed to 3D fluid simulation digital art using BCI. We used Unity3D and MindSet to implement our art work prototype. This study will expand the participation of the spectator in digital art. In addition, it will expand the possibilities of BCI in digital art interaction.