Marshall Test was performed to find out how to improve the application effect of asphalt mixture. The effect of two types of fibers with different contents on Marshall Index was investigated to determine the laws of influence on relevant indexes. The results show that the optimal usage of conventional asphalt mixture is proportional to the amount of fiber added. Specifically, the optimal usage increases with the amount of fibers added. However, when the amount of fibers added exceeds one threshold, the optimal usage remains unchanged. The more the fibers are added, the more obviously the mixture density decreases and the voidage increases. The stability and flow value of mixture increases as the two types of fibers are added. In particular, the stability and flow value undergo a significant increase when the polyester fiber-reinforced mixture is added.