An excavation control system includes a working unit, hydraulic cylinders, a prospective speed obtaining part, a speed limit selecting part and a hydraulic cylinder controlling art. The prospective speed part is configured to obtain a first prospective speed depending on a first distance between the bucket and a first designed surface, and a second prospective speed depending on a second distance between the bucket and a second designed surface. The speed limit selecting part is configured to select one of the first and second prospective speeds as a speed limit based on a relative relation between the first designed surface and the bucket and a relative relation between the second designed surface and the bucket. The hydraulic cylinder controlling part is configured to limit a relative speed of the bucket relative to one of the first and second designed surfaces to the speed limit.