The invention relates to a method for purifying halogenated oligosilanes in the form of a pure compound or a mixture of compounds with respectively at least one direct Si-Si bond, the substituents thereof being exclusively made from halogen or from halogen and hydrogen and in the composition thereof, the atomic ratio of the substituents: silicon is at least 3:2, by the action of at least one purification agent on the halogenated oligosilane and by isolating the halogenated oligosilanes with improved purity. According to prior art, halogenated monosilanes such as HSiCl3 are purified by treating with organic compounds, preferably polymers, containing amino groups, and are separated from said mixtures. Based on the contained amino groups, said method can not be used for halogenated oligosilanes as the secondary reactions lead to a decomposition of the products. The novel method is used to provide the desired products in a high yield and purity without using the amino groups. The purification of the halogenated oligosilanes is carried out in the presence of specific purification agents which transform said contaminations such as for example, FeCl2 into an insoluble and/or less volatile form. Separating the product completes the purification. Said method leads to a higher yield and prevents problems linked to the state of the art such as, for example, long distillation times. Said method is suitable for purifying for example Si2CI6, Si3CI8, Si4Cl10 and higher homologues. These can be used for example in the separation of silicon nitride layers in CVD processes.