UHPC is a new concrete with fine particles and homogeneous matrix, which has high compressive strength and excellent durability against aggressive environments such as chloride ion penetration and freeze-thaw cycles. It’s usual to use the short steel fibers in UHPC. Using fibers causes a significant increase in flexural strength, ductility and energy absorption, and also fibers improves the compressive strength and durability of concrete slightly. Using glass fibers in this concrete is a new work and its advantages, compared to steel fibers are a lower price and be available in the market of Iran. Over time, the glass fibers in the alkaline environment of concrete will be damaged, so affect on the mechanical properties of concrete. In this research, the attempt is to assess the durability of Ultra-High Performance Concrete reinforced by glass fibers under freeze-thaw cycles and accelerated aging. In this research, with doing a lot of laboratory tests, the optimal ratio of water to cementitious materials and proper curing regimes have been selected. Then the effect of using glass fibers in the matrix of UHPC is investigated with two types of curing regimes (Autoclave and Normal) and two types of Pozzolans (Silica fume and Metakaolin) under accelerated aging and freeze-thaw cycles. Using glass fibers in the prismatic specimens of UHPC increases highly the toughness and modulus of rupture. Compressive specimens after 300 freeze-thaw cycles have maximum 6% reduction of strength and flexural specimens have maximum 13% reduction of the modulus of rupture that shows high durability of UHPC reinforced by glass fibers under freeze-thaw cycles. After accelerated aging with hot water, the compressive strength of all cubic specimens has been risen, but specimens without fibers have more increase. After accelerated aging with hot water, modulus of rupture of all prismatic specimens has been reduced. The decrease of the modulus of rupture in samples that contain glass fibers is about 40%. Replacement of metakaolin instead of silica fume, in the matrix of concrete, increases slightly the durability of concrete. Also using Metakaolin causes lower workability of fresh concrete. Key Words: Ultra-High Performance Concrete Reinforced by Glass Fibers, Metakaolin, Silica fume, Autoclave, Durability, Accelerated Aging, Mechanical Properties