Based on the designing scheme of highway widening project, a serial of model tests were conducted to simulate the performance of geogrid reinforced widening embankment influenced by subgrade differential settlement. Totally, 6 models including no-geogrid reinforcement embankment, geogrid reinforcement embankment, differential settlement of 0mm, 20mm, 30mm, and 50mm between existing subgrade and newly widening subgrade were built. The differential settlement distribution of embankment and stress performance of geogrid on each model were tested and analyzed. The test results show that geogrid reinforcement can effectively decrease the vertical deformation of embankment which with load on the top. The heavier the load, the more effective the decrease of vertical settlement. Meanwhile, the geogrid can significantly adjust the distribution of settlement along the cross-section direction of embankment to less differential. The geogrid at the connection area of existing embankment and newly widening embankment receives the biggest tension stress under the subgrade differential settlement. It is suggested that a solid connection between geogrid and the existing embankment is very important for getting a better geogrid reinforcement effect on decreasing the differential settlement between existing embankment and newly widening embankment.