What I should do if no distribution fits my dataset? I need to know what probability distribution represents one variable of my dataset. I've tried some tools in R, such as, rriskDistribution or fitdistrplus and no-results have found. The size is about 26000.
It seems to be a normal but I carried out some test and failed. I give you some examples:


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 A: If you have 26K data, any test on a given distribution will fail. Because for that much data, the testing can detect tiny difference and report it is not coming from that distribution. 
I would strongly recommend you to read these posts
Are large data sets inappropriate for hypothesis testing?
Is normality testing 'essentially useless'?

It is very common that data is not coming from any distribution in text book. But we still can do a lot with it.
For example we can fit data with Mixture of Gaussian model. 

In addition, the distribution of your data seems too good (that coming from normal distribution) that may be coming from some simulation but not from the real world. I would suggest to do following thing: draw 26K sample from normal distribution and run the hypothesis test and all the plots to see the results. This is probability what was happening in your case.
A: You could use Mathematica's FindDistribution command, but the person above who said that with so much data you are unlikely to see any test report that the data is Normal was absolutely correct.  However, FindDistribution almost certainly will return one or more (mixture) distributions that fit fairly well.
I had a similar problem and used Tukey's Fences (Wikipedia) to determine that about 18% of my very large data set was outliers.  It took several months of on and off reflection and reading for me to figure out where the outliers were coming from.  I suggest that you spend whatever time it takes to develop an accurate mental and/or pictorial model of what is going on in the process so that you can explain everything that is going on in your process, including outliers, with a theory. 
A: You got just Two options here:
1.Create a database which fits a distribution.!
2.divide your database (hope it will fit) and run them concurrently and merge later as per your requirement
