The invention relates to a method for preparing star polymers based on a lactide monomer and a glycolid monomer or a lactide monomer, by opening the cycle in the presence of a catalyst, characterised in that: the catalyst is of formula (I) wherein R is a C1-C6 haloalkyl; and the initiator is a polyol comprising between 3 and 6 hydroxyl functions. Said novel method is especially advantageous in that it is easily controllable and is more effective that prior art methods.
