Based on phase noise and phased array antenna theory, using original linear array antenna pattern function and optical fiber link noise figure function, the theoretical formulas that describe relationship between the figure in optical fiber delay line links noise, the number of antenna elements and beam pointing error were derived by reasonable approximation according to actually beam pointing error. The normal optical fiber link parameters were applied to the simulation. The results demonstrated that mean square deviation of phased array antenna beam pointing error increases with the increasing of optical fiber link noise figure and decreases with the increasing of elements number of the array, the phased array antenna beam pointing error is in proportion to 1/2 power of optical fiber delay line links noise figure, in inverse proportion to 3/2 power of number of array elements. In phased array antenna operating frequency bands, it is more obvious impact of optical fiber delay line links noise in low frequency band.