Based on lime simulating active component(SiO2 and Al2O3) of the sludge theory, non calcination sludge brick was prepared in the saturated steam environment. The mechanical properties of lime sludge system with incorporation of fly ash（10%50%） and cement（5%20%） were systematically investigated. Mercury intrusion measurements, scanning electron microscopy, X ray diffraction and ultrasonic pulse velocities were also used to measure the characteristic and evolution of microstructure. The experimental results show that the strength of brick with 30 % lime and 20% cement increases by 50% than the one of pure brick. In addition, brick with 30% fly ash improves the mechanic properties, and reduces pore size and porosity.