To check the accuracy of your assembly, you can calculate the genome fraction and N50  of your contigs assembly file using QUAST tool (http://quast.bioinf.spbau.ru/). 

Contigs with high N50 and high genome fraction is generally considered good. 

Checking the N50 as recommended in the previous answer is a good first step. But there are additional things other than contiguity you want to consider including:

1\ How reliable is the assembly? If you align an independent NGS data from another sample of the same species, do you get high mapping rate, equal and expected coverage? You might get some contigs with unequal coverage suggesting repeat regions and if your sample is diploid or polyploid, some merging might be necessary.

2\ How useable is the assembly? Can you find genes in your assembled sequences? Do you expect these genes in your genome? Are highly conserved genes present in your genome?

To figure out the accuracy of a genome assembly (besides of the N50 etc. for the proportion of the genome assembled etc.), you can use linkage map of the same population to map the markers on the assembled genome and figure out the level of miss-assembly and contiguity in your genome assembled. Reads coverage plot along the genome will also help. Note that the denser you have the linkage map, the better and easier miss-assembly detection and correction.

Thank you so much for your great answers.

Dear researchers,

I have performed an assembly, but after annotating the contings, I found some of the codding sequences are identical. How can I solve this problem?

Regards