I have raw reads of virus data. and I want to assemble the viral genome. any tool / pipeline suggestion and also help me regarding viral annotation as well
Is it genome sequencing or metagenomic dataset? In my experience, SPAdes works well for viral genome assemblies.
this is genome sequencing. I just tried SPAdes but not a good assembly results
What do you mean by a not good assembly? What other pre-processing steps have you performed, e.g. adapter trimming, removing host sequences. It'd be advisable to provide as much information as possible including the sequencing platform, the type of sequencing and a bit about the samples itself. These details would help understand this specific problem better.
For more info on how to ask a good question please read: [ Please read before posting a question ] -- How To Ask A Good Question
If you know which virus it is you could try to find a reference and use BWA
tadpole.sh from BBMap suite works well for small/viral genomes. A guide is available here.