Fatigue damage to asphalt roads under cyclic loads affects traffic and regional development. The deterministic cumulative damage theory is an important tool for studying material fatigue damage. However, owing to the distribution characteristics of asphalt materials and the randomness in the fatigue damage process, the study of random damage is particularly important. Based on the cumulative damage theory of asphalt materials under repeated loads, the random distribution characteristics of asphalt pavement materials and the randomness of actual traffic loads were used to determine the optimal pavement life of asphalt pavement materials under different conditions. A damage model was created based on the probability density functions for various critical damage values and rates. They derived equations for the evolution of the expected fatigue damage and its variance under these conditions, as follows: When the traffic load follows a Poisson distribution, comparing the variability of fatigue damage under different fatigue life distributions to traffic load expectations reveals that a log-normal distribution with similar expected values and variances is suitable for lighter traffic, whereas a normal distribution with a significantly higher expected value than the variance is suitable for heavier traffic. Under the same cyclic fatigue load, the fatigue damage to the asphalt material can vary widely from the expected value. Traditional deterministic damage theories account for only part of this variation, explaining the diversity of parameters in engineering models. The study found that a critical damage value below 0.8 indicates that the material can handle less fatigue load, with little difference between 0.8 and 1. For a better road economy and longer fatigue life, asphalt should aim for a critical damage value of approximately 0.8. In addition, when the damage growth rate was close to 1, the asphalt fatigue damage increased at a slower rate. Finally, the theoretical pavement life calculated in this study was compared with the average maintenance years of actual asphalt pavements using an equivalent formula for traffic load and service life. The study concluded that the theory aligns with reality and that the optimal asphalt pavement service life derived from the random cumulative fatigue damage theory significantly exceeds the actual data.