Abstract: Scanning electron microscope was used to observe the microstructure of cracking Li-Zn ferrite tablets in failure phase shifters, and reasons of its cracking was analyzed. The results show that short of density and uniformity, which constituted the main reasons for the cracking of the Li-Zn ferrite tablets during service process, were majorly resulted from adding PVA binder excessively in suppressing process. Lower sintering temperature which led to inadequate sintering densification and high porosity in the Li-Zn ferrite tablets played the secondary part in cracking causes of Li-Zn ferrite tablets in failure phase shifters. Good PVA amount was 8%(mass) and sintering temperature was 1 020 ℃. Li-Zn ferrite tablets obtained at above conditions would not crack after short term service in phase shifters.