Mathematical computation for a scheme of balanced optical cross correlation and analysis for the effect of the related parameters on the measuring performance are given. The measuring principle is studied in detail and the mathematical computation is given. We analyze the effect of the pulse width,the crystal length and the group velocity difference between the two perpendicular polarized pulses on dynamic range and sensitivity. On the basis of the theoretical analysis,we construct the experimental platform of the balanced optical cross correlator for the first time to measure the timing jitter of the pulses after transmission through a fiber link of 100 m. The experimental calibration curve agrees with our theoretical computation and the rms of the timing jitter is about 20 fs in the frequency range of 1-100 Hz with the existence of the fiber vibration.