Abstract Retinal detachment typically occurs when the retina is pulled away from its normal position by blunt trauma. It has been estimated that traumatic retinal detachments account for 10–20% of all detachments. Understanding the mechanism of traumatic retinal detachment is helpful for ophthalmologists to make a more accurate diagnosis before the symptoms develop. A finite element eye model, validated through published data, was used to simulate traumatic retinal detachment. Retinal adhesive force was incorporated into the model using breakable bonded contact. Under BB impact, global deformation was divided into four stages: compression, decompression, overshooting and oscillation. Shockwave propagation in the retina produced high strain in the retina. For an impact speed of 50m/s, the peak strain of 0.138 in ora serrata exceeded the specified threshold for retinal break. When the eye was decompressed, negative pressure occurred around and anterior to the equator, with a minimum of −663kPa, leading to retinal detachment. The following relative inertia motions between the retina and its supporting tissue extended the detachment. In addition, the simulations of lower shear modulus of vitreous and increased retinal adhesive force also confirm that the extent of retinal detachment is determined by negative pressure and inertial motion. In conclusion, shockwave and negative pressure contribute to retinal detachment. Shockwave propagation in the retina leads to retinal break, while negative pressure and relative inertial motion could pull the retina away from the supporting tissue. The current work would help understand the basic mechanisms underlying blunt trauma.