The invention provides a vehicle-mounted positioning terminal data uploading method and system. The method comprises the steps that the positioning data of a vehicle are acquired; the lateral acceleration value of a vehicle is acquired through an acceleration sensor, wherein the lateral direction refers to the direction perpendicular to the traveling direction of the vehicle; the acceleration value is compared with a preset acceleration threshold, and if the absolute value of the acceleration value is greater than the acceleration threshold, the acceleration duration is calculated; the acceleration duration is compared with a preset time threshold, and if the acceleration duration reaches the preset time threshold, positioning data are uploaded. According to the invention, the problems of poor uploading track continuity, unsmoothness and poor monitoring instantaneity in vehicle positioning monitoring are solved.