diff --git a/dev/merge_spark_pr.py b/dev/merge_spark_pr.py
index a9bf692..c240268 100755
--- a/dev/merge_spark_pr.py
+++ b/dev/merge_spark_pr.py
@@ -610,7 +610,11 @@ def main():
     branch_names = sorted(branch_names, reverse=True)
     branch_iter = iter(branch_names)
 
-    pr_num = bold_input("Which pull request would you like to merge? (e.g. 34): ")
+    if len(sys.argv) == 1:
+        pr_num = bold_input("Which pull request would you like to merge? (e.g. 34): ")
+    else:
+        pr_num = sys.argv[1]
+        print("Start to merge pull request #%s" % (pr_num))
     pr = get_json("%s/pulls/%s" % (GITHUB_API_BASE, pr_num))
     pr_events = get_json("%s/issues/%s/events" % (GITHUB_API_BASE, pr_num))