A measurement method of signal-noise ratio for the single shot laser based on space scanning of optical Kerr gate was presented. In this method, the gate light and probe light transmit orthogonally in optical Kerr medium, the measurement of signal-noise ratio for the single shot laser was achieved by using an optical Kerr gate to make a space scanning for the probe light. With this approach, a single shot laser signal-noise ratio measurement was realized experimentally with a temporal window of 88.2 ps and a resolution of 2.7 ps. This method has no limitation on spectral range because of the gate is controlled by optical Kerr effect.