Provided is a chimeric transcriptional activator for a methanol-inducible promoter, which at least comprises a first portion and a second portion, wherein: 1) the first portion comprises: i) a DNA binding domain; or ii) a DNA binding domain and a first transcription activation domain; and 2) the second portion comprises at least one second transcription activation domain. Further provided is a use of the chimeric transcriptional activator in enhancing foreign protein expression levels in a host cell.