Steel slag is the main solid waste from steelmaking process, which output increases rapidly year after year. This paper sums up the utilization patterns of steel slag both at home and abroad, especially focusing on the development of reuse of steel slag. Basing on those, a new conception of steel slag reuse by adopting slag composition modification and smelting reduction is proposed, the aims of which are recovering the Fe and phosphor from steel slag simultaneously. The slag after treatment can be returned into steelmaking process again, meanwhile a kind of low grade ferrophosphorus as a byproduct will be obtained. Steel slag reuse should meet the request of low-carbon economy, which decreases and restricts the solid waste discharge from iron and steel industry. More costly means for slag treatment to achieve a biggest benefit should be paid attention as possibly.