With the analysis of vehicle longitudinal dynamic model, a modified recursive least squares for online estimation of vehicle mass and generalized slope was established. Compared with the recursive least squares of single forgetting factor, the modified algorithm had better performance in estimation of parameters with different change rates. On the base of that, the self-adaptive gearshift strategies of uphill and downhill slopes were developed. The vehicle road test results indicated that these strategies could improve the slope traveling performance of automatic transmission and overcome the problems encountered by traditional gearshift strategy travels on slopes. 