To fully use the flexible regulation resources of the grid to solve the fluctuation smoothing problem of massive distributed renewable energy clusters(DREC) power generation in the grid, a flexible smoothing method is proposed for the fluctuation characteristics of DREC. Firstly, the method of adaptive gaussian filtering strips out the power for DREC that meets the grid entry criteria and obtains the power generation that needs to be smoothed out; secondly, according to the proposed fluctuation characteristic evaluation index, quantitative analysis and grade evaluation are performed on the stripped power generation that needs to be smoothed out, and the corresponding flexible smoothing strategies are adopted according to the fluctuation grade. Then, corresponding strategies adopt the flexible regulation resources to realize the flexible stabilization effect of DREC. Finally, a simulation analysis is conducted to verify the feasibility and effectiveness of the method by using the power generation data of photovoltaic power plants in a region on typical days.