The invention discloses a low-
orbit constellation phase retention parameter 
estimation method, and belongs to the technical field of 
satellite orbit control. According to the method, the 
orbit semi-major axis measurement value output by 
satellite-borne GNSS 
orbit determination is not directly used, the 
latitude argument measurement value with high precision is used for indirectly estimating the orbit semi-major axis flat root, the 
orbit determination precision of an existing GNSS 
receiver is not improved, the high-precision requirement of 
satellite constellation maintenance on the orbit semi-major axis can be met, and the double-frequency GNSS 
receiver with a higher price is prevented from being configured on a satellite; and after the relative 
latitude argument measurement value is converted into the flat root, polynomial fitting is carried out, then polynomial fitting is carried out on the variation trend of the orbit semi-major axis flat root by utilizing the variation relationship between the relative 
latitude argument flat root and the orbit semi-major axis flat root, and the fitting coefficient is calculated, so that the orbit semi-major axis flat root at any moment is indirectly estimated, the precision of the semi-major axis flat root is superior to 1m, and 
constellation phase keeping can be completed based on a single-side drift ring control strategy under the condition that any semi-major axis attenuation rate is met.