Abstract: Electric vehicles are prone to collision accidents during operation, and power lithium batteries are inevitably subjected to impact. Based on the above background, the study was conducted on the influence of different impact masses on the dynamic impact response and failure behavior of square lithium batteries. By using a drop hammer impact test and adjusting the mass and impact speed of the punch, various impact conditions that lithium batteries may encounter were simulated. The research results show that impact quality and impact velocity are the key factors determining the dynamic failure behavior of lithium batteries. Impact quality is an important factor in determining the degree of damage to lithium batteries. Under the same impact energy, the damage of low-speed large mass impact on lithium battery is significantly higher than that of high-speed low mass impact. At a constant impact energy, mass is the dominant factor in determining the degree of battery damage. If the impact mass is heavier, it will produce a larger impact load, which will cause more serious damage to the internal structure of the lithium battery, leading to its functional damage or even failure. Conversely, if the impact mass is lighter, the impact force generated is relatively small, and the damage to the battery structure is correspondingly reduced. Therefore, the size of the impact mass directly affects the degree of damage to the lithium battery, which is a key indicator for evaluating its safety performance and durability. The impact speed has a significant impact on the voltage drop of lithium batteries after damage. Especially accelerating the occurrence of hard short circuits, further exacerbating the sharp drop in voltage. This characteristic makes the impact velocity as an important consideration for evaluating the voltage stability and overall safety performance of lithium batteries after damage. This study analyzed the failure behavior of square lithium batteries under dynamic impact, providing effective reference for defining the collision safety threshold of lithium batteries, optimizing their safety design strategies, and improving overall safety performance.