The invention provides a titanium dioxide primary product and a preparation method thereof. The preparation method comprises the following steps: (a) mixing metatitanic acid, titanium dioxide sol and a salt solution, and performing suction filtration to obtain a raw material mixture filter cake; and (b) calcining the raw material mixture filter cake obtained in the step (a) to obtain the titanium dioxide powder primary product. The calcining process particularly comprises the steps of sequentially performing dehydration, desulfuration, crystal type transformation and crystal growth on the raw material mixture filter cake to obtain the titanium dioxide powder. Compared with the prior art, the preparation method of the titanium dioxide primary product has the advantages that metatitanic acid and seed crystals are mixed in the salt solution, the calcining process is controlled to obtain the titanium dioxide primary product with high quality index; and the titanium dioxide primary product is high in content of rutile, high and stable in lightening power and whiteness, and good in pigment performance. Experimental results show that the titanium dioxide primary product obtained by the preparation method has the content of rutile of 97.8% or above, the whiteness of not lower than 96.45, the Tcs value of not less than 1958 and the Scx value of not less than 3.67.