A high concurrency access optimization method for NB-IoT network based on multi services was proposed in this paper. When there were a large number of IoT terminals accessing NB-IoT network

the IoT terminals were clustered into different access priority categories by considering the network coverage of the terminal location

the sensitivity requirements of different service terminals to the delay and the waiting delay of the terminal initiating access. After that

the available random access preamble and NPRACH resources were allocated to the terminals in the high access level category to make random access request

which can effectively improve the first access success rate of the terminal and system capacity

and reduce the access delay.