It is NOT a space but a non-printable character.

thanks.
then how to remove it?

First, you can use the substr function to find out what is its value for that space-like character, then compress that value. Example attached below,

data _null_;
     
          z=catt('a', byte(1),'b');
          zsp=compress(z, ' ');

          compvar=char(z,2);
          put compvar= ;   *** see nothing;
      put compvar= hex2.;***see in hex value;
          put;
         
          zsp2=compress(z,compvar);
          put z= zsp= zsp2=;

run;

thank you very much.

I found a sample code at http://support.sas.com/kb/24/716.html

data sample;
  string='Your'||'05'x||'data'||'0D'x||'goes'||'0C'x||'here.'||'0A'x;
run;

data _null_;
  set sample;
  put string=;

  /* Verify each byte in string until no more non-printables are found */
  do until(test=0);

    /* For SAS 9.0 and above, NOTPRINT */
    test=notprint(string);

    /* prior to SAS 9.0, use VERIFY */
    *test=verify(upcase(string),' ABCDEFGHIJKLMNOPQRSTUVWXYZ,.1234567890');

    /* If a non-printable is found...replace it with a space */
    if test>0 then do;
      substr(string,test,1)=' ';
      end;
    end;
  put string=;
run;

楼主说的空格可能只是看起来像空格，其实这个空格的编码和普通的空格是不一样的，可用UE工具查看下

好的，我试试。
同时感谢楼上的各位。