Abstract: To improve the working performance of geopolymer solidified sludge, the single-component geopolymer as sustainable cementitious material was prepared by using various industrial by-products and activators. The influence of hardener amount, activator type and curing age on the strength and micro-structure of single-component geopolymer solidified sludge was investigated by unconfined compressive strength and scanning electron microscope tests. And a empirical strength prediction model for geopolymer solidified sludge was proposed. The results demonstrated that the compressive strength of solidified soil increased with the increasing curing age and dosage, and the turn point of incorporated hardener content and strength growth coefficient of solidified soil were closely related to the activator type. The activation performance of sulfates were better than alkaline activators, and the sequence of various sulfate activators was presented as follows: aluminum sulfate > sodium sulfate > sodium silicate > sodium hydroxide. The C-A-S-H gels promote the micro-structure development of solidified soil and enhance its strength behavior. The ettringite formed in sulfate-activated byproduct system could fill the pore space between particles, furthermore improving the micro-structure and compressive strength of solidified matrix. The parameters in the empirical strength prediction model were closely related to the activator types, and the prediction results were in good agreement with the measured data.