The　influence　of　some　factors　on　synthesis　of　5(6)-carboxy-rhodamine　110　was　investigated,　such　as　reaction　time,　heating　mode,　and　nitrogen　atmosphere.　MALDI-TOF　mass　spectrometry　was　used　for　monitoring　the　synthesis　reaction.　The　optimized　reaction　conditions　are　as　follows.　Under　the　protection　of　nitrogen,　after　reaction　at　80°C　for　1　h　the　temperature　is　raised　to　180°C　at　a　constant　rate　within　30　min.　Then　the　reaction　is　maintained　at　the　temperature　for　6　h.　Under　the　conditions　the　reaction　is　nearly　completed.　A　little　of　sulfonated　derivatives　formed　in　the　reaction　can　be　purified　by　recrystallization.　The　yield　is　93%.　©　All　Rights　Reserved.