A method for crosslinking hyaluronic acid, or one of its salts, and optionally other biocompatible polymers, characterized in that it comprises at least the steps of: a) preparing a first aqueous phase of hyaluronic acid, and optionally of other biocompatible polymers, partly crosslinked, characterized by: - the addition of hyaluronic acid or one of its salts and optionally of other biocompatible polymers, in an aqueous solution in order to obtain a hyaluronic acid concentration C1 - the addition of an amount Q1 of crosslinking agent - achieving partial crosslinking of the hyaluronic acid by controlling the temperature T1 and the duration t1 of the crosslinking reaction, wherein the prepared first aqueous phase of partially crosslinked hyaluronic acid is not converted into particles; b) preparing at least one second aqueous phase of hyaluronic acid and optionally of other biocompatible polymers, partly crosslinked, characterized by: - the addition of hyaluronic acid, or one of its salts and optionally of other biocompatible polymers, in an aqueous solution in order to obtain a hyaluronic acid concentration C2 - the addition of an amount Q2 of crosslinking agent - achieving partial crosslinking of the hyaluronic acid by controlling the temperature T2 and the duration t2 of the crosslinking reaction, wherein the prepared at least one second aqueous phase of partially crosslinked hyaluronic acid is not converted into particles; c) adding the at least one second partly crosslinked hyaluronic acid phase into the first phase, and then producing a mixture of said at least two phases by optionally adding an additional amount Qm of crosslinking agent; and d) continuing the crosslinking of the mixture made beforehand by controlling the temperature Tm and the duration tm of the crosslinking reaction, wherein the crosslinking method does not involve the addition of crosslinked hyaluronic acid particles or one of its salts, or of any other polymer, during steps a, b, c and d of said crosslinking method. a) preparing a first aqueous phase of hyaluronic acid, and optionally of other biocompatible polymers, partly crosslinked, characterized by: - the addition of hyaluronic acid or one of its salts and optionally of other biocompatible polymers, in an aqueous solution in order to obtain a hyaluronic acid concentration C1 - the addition of an amount Q1 of crosslinking agent - achieving partial crosslinking of the hyaluronic acid by controlling the temperature T1 and the duration t1 of the crosslinking reaction, wherein the prepared first aqueous phase of partially crosslinked hyaluronic acid is not converted into particles; - the addition of hyaluronic acid or one of its salts and optionally of other biocompatible polymers, in an aqueous solution in order to obtain a hyaluronic acid concentration C1 - the addition of an amount Q1 of crosslinking agent - achieving partial crosslinking of the hyaluronic acid by controlling the temperature T1 and the duration t1 of the crosslinking reaction, b) preparing at least one second aqueous phase of hyaluronic acid and optionally of other biocompatible polymers, partly crosslinked, characterized by: - the addition of hyaluronic acid, or one of its salts and optionally of other biocompatible polymers, in an aqueous solution in order to obtain a hyaluronic acid concentration C2 - the addition of an amount Q2 of crosslinking agent - achieving partial crosslinking of the hyaluronic acid by controlling the temperature T2 and the duration t2 of the crosslinking reaction, wherein the prepared at least one second aqueous phase of partially crosslinked hyaluronic acid is not converted into particles; - the addition of hyaluronic acid, or one of its salts and optionally of other biocompatible polymers, in an aqueous solution in order to obtain a hyaluronic acid concentration C2 - the addition of an amount Q2 of crosslinking agent - achieving partial crosslinking of the hyaluronic acid by controlling the temperature T2 and the duration t2 of the crosslinking reaction, c) adding the at least one second partly crosslinked hyaluronic acid phase into the first phase, and then producing a mixture of said at least two phases by optionally adding an additional amount Qm of crosslinking agent; and d) continuing the crosslinking of the mixture made beforehand by controlling the temperature Tm and the duration tm of the crosslinking reaction,