How to plot a 3D XY line?
 

http://ugc.qpic.cn/adapt/0/721ad2f6-...03b99bd01d/200
Can someone help me to plot a picture like this?
I don't know how to prepare the data format.

Plotting a 3D line in Tecplot
 

Your question is a basic one, and the answer depends on what you are really trying to achieve. So I will show a simple Tecplot format, and refer you to the user manual here: http://download.tecplot.com/360/current/tpum.pdf to makes plots of increasing complexity.

The 3-D plot you show would have six zones in Tecplot – one for each line. To create one of the lines (or zones) you would have a data file similar to what is found on page 128 of the Tecplot data format manual located here: http://download.tecplot.com/360/current/dataformat.pdf .

Here is an example for the creation of one of the six lines.

TITLE = "Example: Simple 3D Line"
VARIABLES = "X", "Y", "Z", "Density"
ZONE I=4, J=1, K=1, DATAPACKING=POINT
1.0 2.0 1.0 2.21
2.0 2.1 1.0 5.05
3.0 2.2 1.0 7.16
4.0 3.0 1.0 3.66

This data file is in a Tecplot ASCII format (*.dat), and can be directly loaded in Tecplot via the Tecplot data loader.

The next step would be to sequentially load in the remaining 5 lines (or data sets) into Tecplot 360 and create the plot.

BTW … the default view for Tecplot 360 for 3-D plots is to not have the XYZ axis show for a volume plot. To show the XYZ axis go to Plot>>Axis and click on “Show Axis” for each dimension.