Based on methods such as hyperbolic method and exponential curve method, we carried out settlement prediction for soft-soil foundation of a highway, which was treated by surcharge preloading. Influences of starting time, time length from the moment of full loading and time interval were studied for the two methods above. Results show that, as for prediction accuracy, hyperbolic method is more influenced by starting time than exponential curve method. Then, time length from the moment of full loading has great influence on the two methods, and prediction accuracy can be improved with the increase of time length. Finally, two methods are less affected by time interval.