This thesis investigates finding the influential nodes in the location-based social network (LBSN). When the users write comments about a location, it is likely that their writing behavior is influenced by others. We observe the real LBSN data and propose a general method to find the influential nodes in an LBSN. We use the Foursquare data to fit the information diffusion model and compute each node’s influence degree, and use a greedy algorithm to find the set of top-k influential nodes of the LBSN. The set of top-k influential nodes can influence the largest number of nodes in an LBSN. The previously best way to find influential nodes uses the information diffusion model to trace all of the nodes in an LBSN and thus costs a lot of time. This thesis uses the information diffusion model to trace each user’s friends and proposes an algorithm to extract the k nodes with high influence among friends. Compared with the previously best result, we show that our method saves a lot of time and the error of our approximation is small.