NOVELTY - Manufacture of polycrystalline silicon ingot comprises paving seed crystals at bottom of container in polycrystalline silicon ingot growth furnace to form seed crystal layer, loading solid silicon raw materials on seed crystal layer, heating container to melt silicon raw materials and part of seed crystal layer to form a liquid layer, adjusting power of heating devices at top and/or bottom of container to change thermal field in furnace and to form temperature gradient vertical to bottom of container, and crystallizing liquid layer.    USE - Method for manufacturing polycrystalline silicon ingot used for solar cell (claimed).    ADVANTAGE - The polycrystalline silicon ingot produced has low impurity content, the produced solar cell is low in cost and attenuation coefficient, and is high in photoelectric conversion efficiency.    DETAILED DESCRIPTION - Manufacture of polycrystalline silicon ingot comprises:    (A) paving seed crystals at bottom of container in polycrystalline silicon ingot growth furnace to form seed crystal layer, loading solid silicon raw materials on seed crystal layer, heating container to melt silicon raw materials and part of seed crystal layer to form a liquid layer, obtaining solid-liquid interface between unmelted seed crystal layer and liquid layer, monitoring location of solid-liquid interface during heating, and maintaining part of seed crystal layer contacted with bottom of container in solid state;    (B) heating container, maintaining temperature at top of container higher than that of melting point of silicon and temperature at bottom of container lower than that of melting point of silicon to form temperature gradient vertical to bottom of container to melt silicon raw materials and part of seed crystal layer melted, similarly maintaining part of seed crystal layer in solid state, controlling thermal field in polycrystalline silicon ingot growth furnace, and crystallizing liquid layer to form crystallization layer to move solid-liquid interface move in direction far away from bottom of container to complete growth of polycrystalline silicon ingot; and    (C) adjusting power of heating devices at top and/or bottom of container to change thermal field in furnace and to form temperature gradient vertical to bottom of container, crystallizing liquid layer, increasing temperature in container from down to up along direction vertical to bottom of container gradually.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the manufacture of polycrystalline silicon ingot.