Oscillation characteristics and evolution process of large Prandtl number (Pr = 58) nanofluid thermocapillary convection is first reported in this work, and the variation of critical Marangoni number and flow instability under different nanoparticle concentrations is revealed. The results show that, nanofluid thermocapillary oscillatory convection consists of multiple vortices and these vortices migrate periodically from cold wall to hot wall, meanwhile, periodic temperature wave and stream function fluctuation cell exist in the oscillation process. As nanoparticle volume fraction increases, the critical Marangoni number decreases obviously, the oscillatory amplitude first increases and then decreases, and the oscillatory period almost increases linearly. This discovery can effectively promote the active control of thermocapillary convection instability.