The core components of the precision instruments such as spectroscope and spectrograph is grating. And one-dimensional multi-slot transmission amplitude grating is the most simple, and its basic theory is also an important basis used as reference when perform grating design, this shows the important status of transmission amplitude grating in spectroscopy study. In this paper, the theory of Fraunhofer Diffraction in optics was used in introducing the basic conclusion and spectral pattern characteristics, with the concrete experiment the spectral pattern of transmission amplitude grating in the monochromatic light and complex light is showed, then the theoretical analysis was done by mathematical reasoning and numerical simulation, the specific expression of spectral characteristic parameters in transmission amplitude was study to confirm the effects of these parameters on the produced spectral, results show that these parameters are independently. Through these studies, we understand that in the design of gratings should pay attention to the full consideration of these parameters and how to specifically improve the performance of the grating.