Characters of surface subsidence have been researched by means of large solid experiment frame in mining horizontal section top coal caving in steep seams. It is discovered that the subsidence of steep seams is different from subsidence of gently inclined seams. The holes which appear initially will be transfixed and form surface collapse pit in process of mining steep seams. Collapse degree of rocks near roof is larger than rocks near bottom. The surface subsidence has repeating characters; and collapse rock is a declined step distribution as mining inferior sections. Collapse pit with deep groove will be formed at last.