Gold nanoparticles(Au NPs) have been extensively used in optical biosensing and bioimaging due to the unique optical properties. Biological applications including biosensing and cellular imaging based on optical properties of Au NPs will be reviewed in the paper. The content will focus on detection principles, advantages and challenges of these approaches as well as recent advances in this field. Biological nanoparticles including gold nanoparticles (Au NPs) have been extensively used in optical biosensing and bioimaging due to the unique optical properties. Biological content including biosensing and cellular imaging based on optical properties of Au NPs will be reviewed in the paper. The content will focus on detection principles , advantages and challenges of these approaches as well as recent advances in this field.