In this experiment, graphene suspensions are prepared by high speed shearing method, and the prepared graphene is characterized by scanning electron microscopy (SEM), Raman spectroscopy and UV absorption characterization. The results show that graphene solution with good water dispersion can be prepared by this method. Further, nano-silver and graphene solution is prepared by photothermal conversion of nanomaterials. The photothermal conversion characteristics of the nano-silver and graphene solution prepared under the action of different laser powers are investigated. The temperature of low concentration sample solution can reach 28.2 ℃ under the action of laser with wavelength of 808 nm and power of 300 mW for 15 minutes. In theory, the enhancement effect of surface plasmon resonance of nano-silver with different particle sizes on the photothermal conversion performance of graphene is simulated by using finite difference time-domain method. The simulation results are in good agreement with experimental results. In addition, photothermal conversion stability and thermal equilibrium time constant of solutions are compared and analyzed, which proves that the nano-silver and graphene solution has good stability of photothermal conversion.