The invention provides an n-butane isomerization catalyst and a preparation method thereof. The preparation method comprises the following steps: preparing hydroxide by using a coprecipitation method, introducing lanthanum salt to increase the ratio of a tetragonal phase, performing hydro-thermal treatment, drying so as to obtain zirconium oxide which is sufficiently crystallized into the tetragonal phase, soaking to load a sulfate radical and molybdate, roasting so as to increase the acid strength of the catalyst, molding, further soaking into a VIII group metal, and performing synthesis, thereby obtaining the n-butane isomerization catalyst which adopts the tetragonal phase zirconium oxide as a carrier. The n-butane isomerization catalyst adopts the nano-grade tetragonal phase zirconium oxide as the carrier; on the basis of the dry basis of the tetragonal phase zirconium oxide carrier, the n-butane isomerization catalyst comprises the following active components in percentage by mass: 0.5-5.0% of lanthanum, 0.5-2.5% of sulfur, 0.5-2.5% of molybdenum and 0.01-5.0% of the VIII group metal. The n-butane isomerization catalyst is high in isomerization activity and selectivity, good in repeatability and catalysis stability, low in reaction temperature, and still relatively high in n-butane isomerization activity at high temperature.