Abstract: Inflow of FDI brings some effect on economic growth and welfare for host country. Through analyzing on the effects of FDI,we can divide the FDI into two kinds which are“quantitative-type”FDI and“qualitative -type”FDI. Host country can entrust multi-national companies with introducing different type of FDI for its economic growth. According to Principal-agent Theory,we obtained：(1) excessive preference for“quantitative-type”FDI of host country may deteriorate its welfare level,while“qualitative -type”FDI may enhance it;(2) host country should make different policy on different type of FDI,according to the different relationship of marginal costs of the two types of FDI.