how to merge more than two sample in Seurat? I would like to merge more than two sample in the Seurat, and the mergeseurat can only merge two sample. So what should I do now. The screenshot is my script.
You have fed arguments to the MergeSeurat() function that it does not expect. In terms of objects, MergeSeurat() accepts only 2 arguments object1 and object2, please do ?MergeSeurat and see yourself.

Seurat is probably the best documented single cell package, your exact question has its own dedicated vignette: https://satijalab.org/seurat/v3.0/merge_vignette.html

As the vignette above is for Seurat v3 and in case you would like to use Seurat v2:
You can create a named list of Seurat objects to be merged and then use reduce() of the purrr package.

# create a named list of seurat objects to be merged
# code not shown

# optional but probably a good idea
# rename cells using object names as prefix
for (i in names(seurat_object_list)) {
  seurat_object_list[[i]] &lt;- RenameCells(seurat_object_list[[i]],
                                         add.cell.id = i)
}

# merge all the objects in the list
merged_combined &lt;- reduce(seurat_object_list,
                          MergeSeurat,
                          do.normalize = FALSE)