The influence of the modulus, dosage of the modifier and curing age on mechanical properties, mineral component, microstructures and hydration products of modified sludge from reservoirs in the Yellow River Basin were investigated using mechanical strength test, XRD, FTIR and SEM technique. The results show that the modulus, dosage and curing age of the modifier have significant impacts on the mechanical properties of the solidified sludge. The compressive strength of the specimen increases with the modifier dosage and curing age, and the maximum value of compressive strength is 7.13 MPa. The results of XRD, FTIR and SEM show that flocculent geopolymer gel can be formed by the reaction of clay minerals and the modifier, and the material structure became more compact and uniform.