Based on the mechanism of the surface plasmon amplification by stimulated emissions of radiation (spaser), a bowtie nanoantenna structure is proposed for single molecule detection by surface enhanced Raman scattering (SERS). The localized surface plasmon resonance (LSPR) properties and the SERS characteristics of the bowtie nanoantenna are numerically analyzed by the finite element method (FEM). The results show that the LSPR strength and the local electric field intensity of the bowtie nanoantenna can be greatly amplified, and its scattering cross-section and electric field strength are up to 1.1×104 and 1×102 times of the non-spaser bowtie nanoantenna, respectively. Meantime, the maximum SERS enhancement factor is 1016 generated by the bowtie nanoantenna, which is enough to accurately detect a single molecule. Moreover, there is a higher SERS enhancement factor of 1012 on the entire surface of the nanoantenna, which is also sufficient for single bio-molecular detection.