Abstract: Exploring the seawater intrusion mechanism in coastal aquifer with horizontal double fractures is critical for understanding the seawater intrusion mechanism in coastal region. Sand-tank experiments and numerical simulation based on discrete fracture matrix model were performed. The effects of horizontal double fractures with different spatial distribution on the seawater intrusion were analyzed in terms of the saltwater wedge and mixing zone. Results showed that: ① The development of saltwater wedge and mixing zone can be enhanced significantly by the horizontal double fractures. The seawater-freshwater mixing between the fractures is more pronounced. The individual effects of the two fractures are limited to each other. The effects are more significant for the fracture that is horizontally close to the offshore and vertically more close to the middle of the aquifer. ② A higher offshore-side fracture can exacerbate the development of the saltwater wedge and the mixing between fractures. However, the height of land-side fracture has a significant influence only on the tail of the saltwater wedge. ③ When the upper or lower fracture is horizontally closer to the inland, the saltwater wedge becomes wider with the total volume being shrank. However, once they are distributed so far to the inland that being out of the range of the saltwater wedge, the mixing zone area and the width of the saltwater wedge can drop sharply.