The influences of precipitation pH, zirconium salt precursors and the calcination temperatures on the crystal structure and catalytic performance of zirconia in isosynthesis have been studied. The results indicated that the catalytic performance of zirconia in isosynthesis was strongly influenced by the pH of precipitating solution, zirconium salt precursors and the calcination temperatures, However, the crystal phase of zirconia was not so sensitively dependent on the pH. Monoclinic was always the main crystal phase when the value of pH was changed in the range of 6-14. Zirconia prepared from Zr(NO3)(4), ZrCl4, ZrOCl2 were monoclinic/tetragonal, but monoclinic was the dominant phase. Zirconia prepared from Zr(SO4)(2) was a mixture of tetragonal/amorphous. Even trace of SO42- involved in the gel, the crystallization of zirconia was delayed, the phase transformation from tetragonal to monoclinic being inhibited,