Abstract: Vehicle has a high risk of rollover when it drives at a high speed in a curve. A rollover earlywarning algorithm of vehicle in a curve was studied,which firstly analyzed the vehicle stability and then established vehicle lateral acceleration limit equation. Combining with the known road information,for example,the radius of the curve,safe speed and early-warning speed could be calculated before entering the curve. The algorithm had been verified by experiments on a driving simulator with hardware-in-theloop.Resultsshow that the algorithm can succeed in providing early-warning for vehicle which has the risk of rollover,thus avoiding rollover and improving the traffic efficiency in the curve.