In this study, a novel superhydrophobic additive (MPSANS) was developed to enhance the freeze-thaw (F-T) resistance of mortar by modifying mica powder with stearic acid and hydrophobic nano-silica. Firstly, the effects of hydrophobic nano-silica content on the hydrophobic properties of MPSANS modified mortar were studied, and MPSA10NS5 exhibited the best hydrophobic property, the water absorption and water desorption of modified mortar decreased by 65.42 % and 35.84 %, respectively. On this basis, abundant tests were conducted to analyze the effects of MPSA10NS5 content on the F-T resistance of mortar. Analytical findings suggested that MPSA10NS5 noticeably reduced the loss of relative dynamic modulus of elasticity and compressive strength of mortar. Furthermore, the microstructure was determined by using the scanning electron microscopy and mercury intrusion porosimetry. According to the test results, MPSA10NS5 refined the pore structure inside mortar and inhibited the crack development. Meanwhile, MPSA10NS5 effectively reduced the most probable aperture of mortar, resulting in an increase of harmless pores and a decrease of harmful pores.