Univ Sci & Technol China, Dept Modern Phys, Hefei 230026, Peoples R China
; Chinese Acad Sci, Inst Theoret Phys, Beijing 100080, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
Assuming the gauge interactions and gravitation to be unified in the chiral extension of the standard model, our calculations prove that the generation number of quarks and leptons surely is 3. It is also given that the energy scale of unification is 4.4 x 10(18)GeV and the mass scale of leptonic quarks is 10(10)GeV.