Abstract: Exiting parallel DEM preprocessing algorithms that do not consider parallel granularity.This paper presents a parallel DEM preprocessing algorithm with granularity control based on the analysis of the sequential algorithm proposed by Moran and Vezina(M&V algorithm).A Message Passing Interface(MPI) library is applied to implement the parallel algorithm. The parallel performance of the proposed algorithm is assessed by two gridded DEMs with different sizes on a multi-nodeLinux cluster. The application results show that the parallel M&V algorithm can complete the computing tasks when filling sinks and removing flat areas at any granuality，and it outputs an optimal granularity to achieve the best parallel performance for a given DEM dataset.