Abstract: A partially alkoxylated polysiloxane is prepared by using a reactor kettle equipped with a reaction column and a reflux condenser, charging the kettle with a lower alkoxysilane where the kettle liquid is kept boiling, continuously feeding a halogenated lower alkylsilane into the kettle through the column top and continuously feeding a mixture of water and a monohydric alcohol into the kettle in controlled rates, completely alkoxylating the halogenosilane with the alcohol within the column to continuously yield an alkoxysilane, hydrolyzing the alkoxysilane, with the hydrogen halide by-produced during alkoxylation acting as a catalyst, and withdrawing a partially alkoxylated polysiloxane containing less than 5% by weight of the alcohol from the kettle.