This paper presents the advanced motion-constrained AV1 encoder for a 360 8K VR streaming application. Currently, 360 8K VR streaming faces problems in limited network bandwidth, limited server-side computing power that makes difficult to serve ultra-high resolution videos to a large number of clients, and limiting power of a consumer electronic device to decode the stream. We propose a motion-constrained AV1 encoder that can solve these problems. The proposed method is composed of three different restrictions: motion vector search range, AV1 encoding options, and constrained loop filters in the boundary region of tiles. The experimental results show the average BDBR overhead of the proposed method with various tiles is 10.00% with saving 17.30% encoding time compared to the existing AV1 encoder. Also, the proposed AV1 encoder improves the BDBR by an average of 12.50% compared to a motion-constrained HEVC encoder.