Track irregularity is strictly controlled in low-speed maglev system. Vertical defl ection due to vertical temperature diff erence is one of the important factors in track irregularity, which should be considered in structural design. In the fi eld of low-speed maglev, few researches have been developed directly about the measurement of temperature and corresponding eff ect. In this paper, the surface temperature and defl ection of a steel box girder in the low-speed maglev experimental line in Shanghai have been measured for several months. Measured surface temperature data are decomposed into temperature trend and fl uctuating part with wavelet based MRA and the former is highly relevant with local climatic. In the analysis of probability distribution characteristics of the vertical temperature diff erence, three weighted probability models are compared, and the weighted sum model of one Weibull distribution and one normal distribution is appropriate, based on which the standard values of the temperature diff erence with 50-year return period are derived. To determine the correlation between the temperature diff erence and defl ection, scatter plots of equivalent linear temperature diff erence obtained by defl ection and measured temperature diff erence were fi tted, and the results shows an approximate linear relationship.