In order to investigate the moisture diffusion property into asphalt film and analyze the relationship between moisture diffusion parameters and asphalt components, the gravimetric method was used to determine the moisture uptake profiles of asphalt film immersed in distilled water at different immersion times. The moisture uptake profiles were used to fit the Fick and Langmuir diffusion models. The correlation between diffusion parameters and asphalt components was analyzed. The results show that there are two different states of moisture in the asphalt film, mobile phase and bound phase, and measured data of moisture absorption conforms to Langmuir diffusion model. In the initial stage of immersion, moisture diffusion into asphalt film is mainly mobile phase moisture. With the extension of immersion time, the bound phase moisture into the asphalt film increases and gradually becomes saturated. The content of asphalt was positively correlated with the saturated moisture absorption, and the ratio of adsorption coefficient to desorption coefficient was linearly correlated with the saturated moisture absorption.