In order to increase the detection efficiency and also reduce the interdetector spillage, a new wedge-shaped BGO scintillation detector array is proposed. By shaping the front part of a detector as a wedge, the absorption path becomes longer, particularly for obliquely incident photons, thereby improving the uniformity in the sensitivity for the incident photons of different angles. To demonstrate the effectiveness of the proposed detector shape, a Monte Carlo simulation was performed and the results are presented.