I have a pool and there s a lot of little mosquito larvae in it. Is there any way I can clean it without pouring out the water?

Mix a bunch of bleach in it

Yes. Buy pool chlorine and the strongest shock treatment you can find and buy enough for the number of gallons of water your pool takes. Pour both into the pool and spread it around by walking around the pool. The chlorine will kill all the mosquito larvae and anything else in the pool. Then put in an algae killer by placing it in a bucket of water and spread it around the pool. Let the chemicals set for a day and then sweep everything on the bottom of the pool from the shallow end to the deep end and when the leaves and such settle on the bottom, vacuum the pool without the debris going into the filter. Bypass the filter and get the dirt and leaves out before using the filter or you’ll have too much junk in the filter. It will most likely take more than one vacuuming to get the job done well. Let the pool sit and clear up for a couple of days and if the water’s cloudy, add a chemical to the water that will make the water clearer. Test the water for the correct chemical balance and either adds more chlorine or muriatic acid to the water. I suggest not swimming in the pool until the correct chemical balance is set. I have to do the same to my pool but I don’t want to because we don’t use the pool and haven’t used it for over five years. The past year is the only year I haven’t kept the pool clear and now there’s algae all over the sides and the bottom. I may have to drain the pool to rid it of the algae. I keep putting it off because I don’t care about the pool and want it gone but it costs a fortune to get it removed so I’ll just pour in the chemicals and not worry about anyone getting into the pool and getting a chemical burn. Nobody has been in the pool for over five years and nobody is going to be in the pool for at least another five years. We can both have fun cleaning our pain in the a*s pools.

sure, overflow the pool (over fill it), use a mesh screen to help get the larvae and put in a lot of chorine bleach

Yes. You can get “mosquito dunks”, They dissolve, releasing Bacillus thuringensis israliensis (Bti), which will kill them and a few related flies, nothing else.