The present invention relates to a liquid composition comprising a monomer, a (meth)acrylic polymer and a multistage polymer. In particular the present invention it relates to a liquid composition comprising a monomer, a (meth)acrylic polymer and a multistage polymer that can be used as a syrup and especially as a syrup for impregnation and for the preparation of for reinforcing the impact strength of a thermoplastic material obtained after polymerization of the syrup. The invention also relates to a process for manufacturing such a syrup. The invention also relates to a process for impregnating a fibrous substrate of long fibers with said viscous liquid syrup. The invention also relates to a fibrous substrate preimpregnated with said syrup which is useful for manufacturing composite parts. More particularly the present invention relates also to a process for preparing a liquid composition comprising a (meth)acrylic monomer, a (meth)acrylic polymer and a multistage polymer.