a random distribution of RA&Dec How to make random positions in Equatorial coordinate system?

If I divide Dec between -90 and 90 evenly, the space distribution is not random.
Well, your problem is that you have a sphere. To compensate for the polar declination skew, you just calculate $$\sin^{-1}(\mathtt{rand})$$
Where $\mathtt{rand}$ is a number in an evenly divided -1 to 1 range. Alternatively, you can use another trigonometric function based on what you have available, but you get the idea.

RA can obviously be divided evenly.