I want to design this kind of steel truss in Staad Pro Connect Edition, should i run analysis in staad space or staad plane which one is correct?
You are only giving a hint with a photo of a screen, but it seems that you have a model which is curing in 3D space. If so you clearly should model this using a STAAD SPACE model. To be perfectly frank, nearly every model constructed in STAAD.Pro today for a commercial project is defined as a SPACE model. The use of 2D PLANE and TRUSS modelling, although still supported by STAAD, is really only used in the academic arena to help explain the basic principles of stiffness relationships and matrix formulations to students before the progress to a 2D space projects.