The force state and the rotational motion of single steel fibre in cement paste subjected to magnetic force caused by external uniform magnetic field were analysed. The relationship among the rotating accelerated angular velocity of steel fibre and the magnetic induction, working time of magnetic field was obtained. Based on this relationship, the magnetic induction and working time of magnetic field were calculated according to the designed orientation of steel fibre, and the preparation conditions for aligned steel fibre reinforced cement paste was confirmed. Based on the theoretical calculation result, an aligned steel fibre reinforced cement paste specimen was prepared using external uniform magnetic field with magnetic induction 113×10-5T for 60s, the orientation distribution of steel fibres in cement paste specimen was tested. The test results show that for nearly 80% of steel fibres in the cement paste specimen, their orientations are in close agreement with designed orientation, and the orientation factor of steel fibres reaches 0968.