The pineapple leaf fiber is abundant in the tropics and subtropics regions in the world. The raw pineapple leaf fiber needs to be degummed before spinning. In this paper, the effect of alkali treatment on fiber property was studied. Compared to the fiber that not treated by alkali, fiber property improved by alkali treatment. At the same time, the influence of parameters of alkali treatment on fiber property was also discussed. With the concentration of sodium hydroxide solution increasing, the fineness, the tenacity, and the breaking elongation of pineapple fiber are all decreased. The effect of time on the fineness of degummed pineapple fiber is insignificant. With the increase of time, the tenacity of pineapple fiber is decreased slightly. However, the breaking elongation of pineapple fiber decreased at first, and then increased. As the temperature increase, the fineness of pineapple fiber increased then decreased. On the contrary, with the temperature increasing, the tenacity of pineapple fiber decreased firstly, and then increased. The breaking elongation of pineapple fiber decreased with the increase of temperature.