The invention discloses a height adjustment system of a vehicle seat, consisting of a front height adjustment device, a rear height adjustment device and a height adjustment handle mechanism, wherein the front and rear height adjustment devices have same structures and are arranged opposite to each other; a left structure and a right structure of the front height adjustment device are symmetric; the right structure of the front height adjustment device consists of a toothed plate and an upspring mechanism; when a handle of the height adjustment handle mechanism is pressed forwards or backwards, the front and rear height adjustment devices can rise or fall at the same time and be locked; and the specific height can be adjusted at random according to the actual requirement. The height adjustment system accords with the human engineering and can satisfy the requirement of drivers with different heights to the height of the vehicle seat so that the drivers can ride comfortably, the healthof the drivers is not influenced by long-term driving and the probability of traffic accident is decreased.