The　effect　of　droplet-like　phase-separation　on　nucleation　was　studied　by　HREM　and　other　analysis　methods　for　K2O-MgO-Al2O3-O-2　glass　system　containing　fluorine　or　zirconium.　It　was　observed　that　the　nucleation　began　in　the　droplet　phase　firstly.　The　effect　of　phase-separation　on　nucleation,　bulk　nucleated　crystallization　and　sequence　of　crystallization　was　analysed　by　means　of　selected　area　electron　diffraction,　lattice　fringes　analysis　and　calculating　distance　between　two　crystal　planes.