Abstract: Hulun lake， the largest inland lake in Inner Mongolia， had suffered a 15\|year lake retreat from 1998 to 2012. The lake retreat had formed a 5 km×3 km rectangle shape wetland. The vegetation of the rectangle shape wetland was investigated in mid\|August， 2012. With the help of spatial sequence instead of time successional sequence method， the succession sequence of the sample spot was revealed. After two\|way indicator species analysis （TWINSPAN）， 70 sample plots had been divided into 6 groups in Division 5 level. Detrended correspondence analysis（DCA） was also adopted and the successional sequence was revealed as Chenopodiaceae pioneer community （first stage）→ Phragmites australis community （second stage）→ Leymus chinensis community （final stage）. After comparing each succession stages biodiversity index （Patrick， Simpson， Shannon\|wiener and Pielou indice） and growth style， it was shown that: （1） The final stage of the succession had the highest biodiversity， evenness and richness; （2） The evenness of the vegetation dropped down a little from the first stage to the second stage， and recovered in the final stage; （3） The proportion of the perennial plant steadily increased from stage one to final stage .

Key words: spatial sequence instead of time successional sequence, TWINSPAN, DCA；vegetation succession, Hulun Lake