skylight hardly effect landscape shadow

my tower is lightened but landscape still dark

Well it looks like your sky itself is pretty dark, so it makes sense that the skylight would be too. If you want it brighter, couldn’t you just increase the intensity further?

Try using a custom cubemap for the skylight and play with it’s intensity. That or play around with the “lower hemisphere is solid color” settings; as in try turning it on and off and/or change the color.

theres a lot here that could be causing this …
lighting source (directional, spot, etc)
material (landscape)
culling of camera
shadow distance
shadow hardness @ distance
… theres a ton in there that can cause this and without knowing your exact setup (other than default changes made) it would be pretty hard to call what is causing it.

im going to guess, by what i see, your lighting is jacked up. maybe thats how you want it, but, its really dark anyways. Lets be honest, its pretty much a night scene in the screenshots. Tons of dark oranges and blacks. Very little (from what i can see) light at all. The first pic with 0 looks fairly “even” with the shadowing. Its looking pretty natural for the sky the way it is. Hard to tell with 2 objects as ref. and a tiny bit of black/orange sky.
0 your shadows are DARK
12 your shadows are slightly less dark, but, not by much
but …
then your tower lightens up, but, not your shadows in the same way … so … im guessing your lighting and skylight have a bunch of random changes made for the visual effect you wanted, but, its not jiving with each other.

thanks you guys,i dont even know the skylight is depending on the sky= =,i made a material for the sphere insteaf of the skysphere blueprint,it still matters?
in my situation,i need to cross a rift behind the if i dont use the skylight lightening the scene,the road would be too dark to get making a darksoul fan-made scene,its not a night scene but dark is the theme:(