Zy Lin,
Please mention the working environment of board and source code details.
1. Are you using TI board like LCDKC6748 or your own custom board?
2. Is that your own custom code?
TI have provided the sample application source code for SPI with EDMA.
Pleas have a look at the below path (If you have StarterWare package)
pdk_C6748_x_x_x_x\C6748_StarterWare_xx_xx_xx_xx\examples\lcdkC6748\spi_edma
I hope, this will help you.