Disclosed herein is an economically viable co-process for converting biomass to liquid biohydrocarbon fuels and for upgrading heavy deteriorate petrol-oils to high value transportation fuels. In the process, cellulose, hemi-cellulose and lignin, which are composed of ligno-cellulosic biomass, are converted to the bio-hydrocarbons (alkanes and aromatics) that are currently derived almost exclusively from fossil fuels. The resulted hydrocarbon liquid can be separated against their boiling points for gasoline, diesel and heavy oils. The heavy oils can then cracked into lower molecular weight hydrocarbons. Meanwhile, the co-processed heavy petro-fuels are partially converted into lower molecular weight hydrocarbons that fall in the boiling point range of gasoline and diesel.