采用超滤将竹浆黑液接枝磺化产物(GCL1-JB)分成4个不同分子量范围的级分，采用凝胶渗透色谱进行分子量表征，研究了不同分子量级分对水泥净浆和砂浆性能的影响。结果表明，高分子量级分对水泥净浆和砂浆的减水分散性能优于低分子量级分，高分子量级分(大于50 000)在掺量0.5%时，水灰比为0.29的水泥净浆流动度为287 mm，120 min经时流动度损失为7%，3 天、7 天和28 天砂浆抗压强度比分别为159.4%，193.4%，143.8%。中等分子量级分具有很强的引气性和缓凝作用，可改善新拌砂浆的工作性，但是硬化砂浆后期的抗压强度低于空白砂浆。中分子量级分(10 000~50 000)在掺量0.5%时，水泥净浆初凝时间延长140 min，终凝时间延长297 min，28天砂浆抗压强度比为99.8%。

Bamboo pulp black liquor modified by graft sulfonation（GCL1-JB） was fractionated into four fractions with different relative molecular mass（RMM） by ultrafiltration,and the RMM distributions of GCL1-JB fractions were characterized by means of GPC.Then,the effects of GCL1-JB fractions on the performances of fresh cement paste and mortar were analyzed.The results show that（1） the fraction with high RMM is of better water-reducing dispersion performance;（2） when the dosage of the fraction with high RMM（more than 50000） is 0.5%,the fluidity of cement paste reaches 287mm at a water to cement ratio of 0.29,the fluidity loss ratio reaches 7% after 120min,and the 3-day,7-day and 28-day compressive strength ratios of mortar are respectively up to 159.4%,193.4% and 143.8%;（3） the fraction with moderate RMM is of strong air-entraining and retarding effect,which improves the workability of fresh mortar,although the long-term compressive strength of hardened mortar is relative low;and（4） when the dosage of the fraction with moderate RMM（10000～50000） is 0.5%,the initial setting time and final setting time of cement paste prolong for 140 and 297min,respectively,and the 28-day compressive strength ratio of hardened mortar is up to 99.8%.