Attitude determination and structural health monitoring system based on GPS multi-antenna has the advantages of fast speed, high precision and continuous working. However, the conventional systems usually use cable to connect antennas and receivers. A GPS-over-fiber multi-antenna receiver system is experimentally demonstrated. Thanks to the advantages of small size, light weight, low loss and immunity to electromagnetic interference of the optical fiber, the proposed system can achieve longer baseline and larger measuring areas than conventional systems. Parallel decoding algorithm is also applied in the proposed system. It can avoid cycle slips introduced by the signal switching in the conventional GPS multi-antenna system. The complexity of data processing algorithm is thus reduced and the efficiency and measuring precision are improved significantly. Experimental results show that the proposed GPS-over-fiber multi-antenna receiver system can measure the baseline accurately and the measurement error is only a few millimeters. The system can be potentially applied to attitude determination and structural health monitoring.