The effect of microfiber produced from recycled waste catalyst on microstructure and mechanical strength of cementitious complex binder was analysed. Complex binder reinforced with 1%, 3% and 5% fibers were exposed to 600, 800 and 1000°C for 3h. The influence of annealing temperature on morphology of fiber reinforced complex binder was analyzed applying SEM, XRD techniques. Experimental results showed that reinforcement with 1% of fiber had advantage on mechanical strength of complex binder up to 800°C. Meanwhile addition of 5% of fiber resulted in lowest values of strength and reduced bulk density of complex binder in all firing temperature range.