Laser-induced air plasma is produced by focusing an 1064 nm Nd:YAG laser beam (spot diameter of 100 μm , pulse energy of 60 mJ, pulse width of 200 ps). The electron density distribution is diagnosed by holographic interferometry. The displacement isoline is obtained from infinite interferogram, and the electron density distribution is calculated from finite interferogram. The results indicate that the ion and electron in laser-induced air plasma form in an olivary shape, which has symmetrical distribution in the vertical direction but unsymmetrical distribution in the horizontal direction, and the maximal electron density is about 1018 cm-3.