The time and spatial-resolved emission spectrum in laser-induced Al plasma was measured for the 390.068,394.4,396.152 and 466.3056 nm spectral lines. The electron density of the plasmas was calculated from the measured spectral line intensity and Stark broadening of emission spectral lines respectively. The time and spatial evolution property of the electron density was discussed according to the experimental results. It is shown that the plasma electron density varies from 0.02×10¹⁷ to 1.4×10¹⁷ cm^-3 when the time delay is in the range from 100 to 1500 ns. It is also concluded that the plasma electron density varies from 0.28×10¹⁷ to 0.95×10¹⁷ cm^-3 along the direction on the laser beam when the distance of the measured zone from the target surface is in the range from 0 to 1.8 mm. The distribution of the plasma electron density along the direction of the laser beam has well symmetry.