A kind of transistor based on graphene heterojunction thin film was introduced， which was fabricated by femtosecond laser technology. According to the principle of preparing graphene by reducing graphene oxide， the graphene was directly prepared on the substrate of Si by femtosecond laser. Finally， the graphene hetero junction thin film transistor （GHTFT） obtained a current on-off ratio of 3.05 × 10². Compared with the graphene transistor before， this value increased by 10². At the same time， the relationship between the current on-off ratio of GHTFT and reduced graphene oxide with different levels was studied. The results showed that with the higher level of reduced graphene oxide， the current on-off ratio of GHTFT was greater， which indicated that femtosecond laser could effectively adjust the electrical properties of GHTFT. In addition， because of the difficulties in preparing graphene at present， the method mentioned in this paper could effectively avoid the transfer process and chemical process. And due to high efficiency， the femtosecond laser could also improve the preparation efficiency of graphene transistors.