Alright, to answer that, we might need to know what might cause lag in a map.
1. Large amounts of abilities being cast such as Volcano, Earthquake tornado and some other ultimate's might make the game laggy.
2. Large amounts of units also contribute to the lag.
3. Instant spawn's, for example, a sudden spawn with 80 units might cause a large lag burst.
4. Large amounts of doodads sometime's cause lag, try removing un-nesscary doodads that dont contribute much to the terrain.
5. Several trigger's running at once and doing multiple functions. Yes, i've done it and it sometime's does cause lag.
6. Trigger's intiated at map intilization. Try not to put trigger's right when the map starts, do elapsed time - 3 seconds or so in the event.
These are what usually cause maps to lag. Atleast the one's that i know of. Try doing the following in what ever map you are making. If none work, list the trigger's, things and such in your map. And we will figure out which one causes the lag.