The invention discloses a network 
system for providing 
mobile edge computing service and a service method thereof, so as to solve the technical problem of flexible deployment of MEC on a 
mobile communication network. In the C-RAN architecture, an SDN-based MEC controller is deployed, and an MEC 
server is deployed in the BBU. The 
service implementation step mainly comprises the following steps: setting a 
decision threshold; judging whether the time 
delay is sensitive or not and the like to determine a computing mode by an MEC controller; and giving a computing result through four computing 
modes of computing of a local MEC 
server, combination computing of a plurality of MEC servers, computing of a specific non-local MEC 
server and computing of a cloud center; and finishing all user MEC tasks through repeated executions. According to the method, the MEC service is realized; meanwhile, the remaining computational resources in the BBU can be sufficiently used, and the MEC network hierarchyis more concise, so that the management is facilitated, the 
data transmission efficiency is improved, the pressure of a 
core network is relieved, and the overall computing task time 
delay is reduced.The method can be used for flexible deployment of the MEC on the 
mobile communication network in the present 4G period, the 4G to 5G transition period and the 5G period.