Nanoparticles　have　attracted　widespread　interest　in　molecular　biology　and　medicine　fields　for　diagnostic　application　and　biological　imaging,　due　to　their　unique　optical　properties　and　facile　surface　chemistry.　Noble　metals,　especially　gold　nanoparticles　(NPs),　have　great　potential　use　in　biological　issue　imaging,　cancer　diagnosis　and　therapy　because　of　their　surface　plasmon　resonance　(SPR)　and　strong　absorption　induced　luminescence.　Au-ligand　conjugates　can　specifically　target　the　receptor　on　cancer　cells,　provide　specific　information　about　specific　molecules,　and　allow　molecular-specific　imaging　and　cancer　detection.　Gold　NPs　can　strongly　absorb　light,　efficiently　convert　optical　energy　into　localized　heat,　produce　selective　photothermal　effect,　and　induce　protein　denaturation　and　cells　death.　The　optical　and　photothermal　properties　of　gold　NPs　are　summarized,　and　the　research　progress　of　selective　targeting　of　gold　NPs　in　biological　imaging,　cancer　diagnoses　and　photothermal　therapy　is　reviewed.