Abstract: Ulansuhai Lake is a typical shallow lake located in a cold and arid region. We have simulated its ice thickness in winter time using an empirical degree-day model based on its daily temperature data and nutrients concentration in the ice seasons from 2007 to 2014, focusing on ice cover impact on the trophic variation of shallow lakes. The results show that the growth in the lake’s ice cover is controlled mainly by thermal process and this degree-day model gave a satisfactory prediction of the maximum ice thickness for each year that is rather close to the measured values. For the period of 2007-2014 when the ice thickness took a decreasing trend, the simulations reveal the corresponding variations in nutrients concentration of this shallow lake in winter season. And using these results, we can explain why the longest ice cover in the years of 2008 and 2012 is possibly connected to the events of spring algal bloom in these two years. This study provides new ideas for water environmental protection and health warning of shallow lakes in cold and arid regions.