The method of magnetic stirring combined with ultrasonic dispersion and addition of polycarboxylic acid water reducer was used to improve the dispersion and stability of nano-TiO₂（NT） in cement paste， and the effect of different content of NT on the mechanical properties of cement paste was studied. Measurement of hydration heat， thermogravimetric-differential scanning calorimetry （TG-DSC） and mercury intrusion method（MIP） were used to study the influence mechanism of NT on cement hydration performance. The results show that dispersion and stable NT suspension can be prepared by adopting magnetic stirring for 20 minutes， ultrasonic dispersion for 15 minutes， and magnetic stirring for 15 minutes， supplemented with polycarboxylic acid water reducer. When the content of NT is 2%， the compressive strength of cement paste is the largest， and under the condition of the same NT content， the mechanical properties of cement paste prepared with the suspension are higher than that of the dry mixing method. NT can significantly shorten the induction period of cement hydration， increase the rate of early cement hydration heat release， change the crystallinity and orientation of CH， optimize the internal pore structure of the hardened cement paste， and improve its mechanical properties.