This summary is based on the work of February, which is focused on reading papers about Ad hoc network and getting familiar with the domain before the research of the Master Subject “Multi-path Routing Protocol for Mobile Ad Hoc Network”. Mobile Ad hoc network (MANET), also called self-organized network, is a multi-hop wireless network where nodes can move arbitrary in the topology. It consists of a set of wireless nodes which dynamically exchange data among themselves without reliance on some fixed base stations or a wired backbone network. It has great differences between the wired network, including the unpredictability of environment, the unreliability of wireless medium, the resource-constrained nodes, the dynamic topology, limited bandwidth, and limited security [6]. Because of the features of the MANET, the research of the routing protocol has been one of the most concerned topics in the MANET. The conventional routing algorithms for wired networks are not efficient for the dynamic changes. For the recent years, people have developed a lot of routing protocol which can be used in MANET, and here some typical protocols are summarized. The rest of the summary is organized as follows. In Section 2, the uni-path routing protocol is introduced, which includes reactive routing, proactive routing and hybrid routing. We introduced some multi-path routing protocols in Section 3. Most of them is developed from one of the uni-path routing protocols, which multi-path is implied to improve the reliability, the end-to-end delay or bandwidth, etc. Section 4 is some issues to be discussed or to be solved for multi-path routing. Sections 5 is some ideas and consideration about the multi-path routing, and in Section 6, some simulation problems and NS2 is discussed.