Heteroepitaxial diamond films were grown on Si(100) via electron emission with a bias voltage, by using microwave plasma CVD and hot filament CVD. The piezoresistivity and magnetoresistivity of p type diamond films obtained by the cold implantation and rapid annealing have been investigated.The experimental results show that epitaxial diamond films have pronounced piezoresistivity and magnetoresistivity effect and can still be operated under extreme conditions such as high temperature, heavy radiation and a strong chemical corrosive environment