We present in this paper the temporally and spatially resolved feature of the side scattered 3ω0/2 harmonic emission, induced by A single laser spot with ten-micron-radius-scale in a preformed laser plasma. The close relation of the harmonic emission with such a small scale laser self-focusing filamentation has been discussed in detail. It is suggested that the side scattered harmonic signal from a underdense region as low as 0.05nc may be caused by the Lang-muir wave and/or ion-acoustic wave scattering induced by laser dynamic filamentation.