To synthesize zeolite A, natural zeolite treated with 6N-$H_2$S$O_2$ solution at 10$0^{circ}C$ for 24hrs was used as a silica source. With the increment of the ratio of natrual zeolite/NaAl$O_2$ ratio, synthetic zeolite A converted to hydroxysodalite and with the increment of reaction time, the crystallinity of zeolite A increased and reached a maixmum at 10$0^{circ}C$after 3hrs and the crystal was converted to hydrosodalite after 5hrs. As the reaction temperature increased, the crystallization rate of zeolite A was increased. In this study, the optimum syntheric condition of zeolite A was the reaction of natural zeolite : NaAl$O_2$: $H_2$ O=1:0.6:8 at 10$0^{circ}C$ for 3hrs.