In. the target experiment by multi-beam irradiation time-synchronization is very important. Using a method of two-photon fluorescence (TPF), we have measured the time-synchronization of six beams Nd3+ glass high power laser system (6 X 1011 W). The active-passive mode-locked Nd3+: YAG oscillator of the time-synchronization was used as the light source for the time-synohronization measurement. The pulse width was 20 ps. Time-synohronization for two opposite beams was measured using a TPF cell capable of four beam transmission on the position of target. Time-synohronization for two crossed beams was measured by placing a half-transparent film on the target position and a TPF apparatus. The measurement is simple and perceivable. The error in the measurement of the time-synohronization by two-photon fluorescenoe is presented. The error is about 4ps for two opposite beams and 5ps for two crossed beams. The total error of the time-synchronization for six beams is about 10 ps.