When the shower is running,we hv water leaks downstairs by our bathroom.will stop leak do the job?

Where would you put the stop leak? It could be a leak in the shower pan, in the drain system, in the valve stem or piping above the valve. Remove the drain cover, tightly shove a rag in the hole, turn the water on and put water in the shower. Turn off the water. If the water doesn't run out, it's probably not the pan. If the leak stops when the water is turned off, it's in the valve or shower piping above the valve. If the water drains out of the shower pan, it's in the pan. You can also cut a hole in the ceiling under the pan and another one in the wall behind the shower control and look for leaks that way.