diff --git a/egs/aishell2/s5/local/prepare_dict.sh b/egs/aishell2/s5/local/prepare_dict.sh
index d59585273a7..56ab885ae94 100755
--- a/egs/aishell2/s5/local/prepare_dict.sh
+++ b/egs/aishell2/s5/local/prepare_dict.sh
@@ -10,7 +10,7 @@
 download_dir=data/local/DaCiDian
 dir=data/local/dict
 
-if [ $# -ne 1 ]; then 
+if [ $# -ne 1 ]; then
   echo "Usage: $0 <dict-dir>";
   exit 1;
 fi
@@ -18,7 +18,9 @@ fi
 dir=$1
 
 # download the DaCiDian from github
-git clone https://github.com/aishell-foundation/DaCiDian.git $download_dir
+if [ ! -d $download_dir ]; then
+  git clone https://github.com/aishell-foundation/DaCiDian.git $download_dir
+fi
 
 # here we map <UNK> to the phone spn(spoken noise)
 mkdir -p $dir
@@ -27,21 +29,9 @@ echo -e "<UNK>\tspn" >> $dir/lexicon.txt
 
 # prepare silence_phones.txt, nonsilence_phones.txt, optional_silence.txt, extra_questions.txt
 cat $dir/lexicon.txt | awk '{ for(n=2;n<=NF;n++){ phones[$n] = 1; }} END{for (p in phones) print p;}'| \
-  sort -u |\
-  perl -e '
-  my %ph_cl;
-  while (<STDIN>) {
-    $phone = $_;
-    chomp($phone);
-    chomp($_);
-    $phone = $_;
-    next if ($phone eq "sil");
-    if (exists $ph_cl{$phone}) { push(@{$ph_cl{$phone}}, $_)  }
-    else { $ph_cl{$phone} = [$_]; }
-  }
-  foreach $key ( keys %ph_cl ) {
-     print "@{ $ph_cl{$key} }\n"
-  }
+  perl -e 'while(<>){ chomp($_); $phone = $_; next if ($phone eq "sil");
+    m:^([^\d]+)(\d*)$: || die "Bad phone $_"; $q{$1} .= "$phone "; }
+    foreach $l (values %q) {print "$l\n";}
   ' | sort -k1 > $dir/nonsilence_phones.txt  || exit 1;
 
 echo sil > $dir/silence_phones.txt
@@ -49,9 +39,8 @@ echo sil > $dir/optional_silence.txt
 
 cat $dir/silence_phones.txt | awk '{printf("%s ", $1);} END{printf "\n";}' > $dir/extra_questions.txt || exit 1;
 cat $dir/nonsilence_phones.txt | perl -e 'while(<>){ foreach $p (split(" ", $_)) {
-  $p =~ m:^([^\d]+)(\d*)$: || die "Bad phone $_"; $q{$2} .= "$p "; } } foreach $l (values %q) {print "$l\n";}' \
+  $p =~ m:^([^\d]+)(\d*)$: || die "Bad phone $_"; if($p eq "\$0"){$q{""} .= "$p ";}else{$q{$2} .= "$p ";} } } foreach $l (values %q) {print "$l\n";}' \
  >> $dir/extra_questions.txt || exit 1;
 
 echo "local/prepare_dict.sh succeeded"
 exit 0;
-