Neural network model is one of the most commonly used techniques in relation extraction. However， the existing neural network models seldom consider the structural features between two entities in a sentence. Based on the characteristics of relation extraction task， this paper proposes a sentence structure acquisition method on neural network model. In this method， the positions of two entities in relation instance are marked so that the neural network model can effectively capturethe structural information about the entities in sentences. In order to verify the effectiveness of the proposed method， two mainstream neural network models are used for comparative experiments. Experiments show that the performance is improved significantly on ACE 2005 Chinese corpus. The result has exceeded the comparison work by approximately 11 percentage points. That proves that this method can significantly improve the performance of relation extraction.