Effect of four fertilizing modes (CK,A1,A2,A3) on bio-mass,sugar contents and the activities of sucrose-metabolizing enzymes of two sweet sorghum varieties（XT-2 & T601）were researched by using field experiment.Result showed:(1)The fertilizing modes had not an effect on growing days.The bio-mass of XT-2 in topdressing treatment A3 with N,P,K fertilizer was the highest,it was 54 916.96 kg/hm²,the bio-mass of T601 in full base P,K fertilizer treatment A1 was the highest,it was 64 136.60 kg/hm²,their yield increasing rates to CK were 14.96%,10.48%,respectively.(2)The changing trends of total sugar content and sucrose content are basically identical.The sugar content in jointing stage was lower,total sugar accumulated the highest value in flag leaf stage.The total sugar content of XT-2 in A3 treatment was the highest,it was 12.7% FW;(3)The effect of fertilizing mode on SPS & SS enzyme activities in stem was very obvious,SPS and SS activities of T601 A3 and XT-2-A1 were the strongest,they were 266.74,431.21 mg·g^-1·h^-1,respectively,and significantly different to other treatments.The fertilizing mode significantly increased the bio-mass,the sugar contents and enzyme activities(SS and SPS) of sweet sorghum.By this way the quality and yields were increased effectively.