Abstract This paper presents the time resolved spectrum with high temporal resolution (～10ps) and spectral resolution (～ 0.6?) of 2ω0 harmonic emission at 90°to the laser axis. It is shown experimentally that the primary peak and the secondary peak of 2ω0 harmonic are actually composed of many fine and bright fringes with the interval about 1.5 ～ 3? directly connected with atomic weight. Analysis and discussion on these are given.