With the advantages of wide coverage, low power consumption, massive user access, Narrow Band Internet of Things(NB-IoT) has become one of the mainstream technologies of wide area IoT. Nevertheless, a single NB-IoT network in the environment with power extremely constrained(such as wells, underground garage in demand of deep coverage) will still have problems of weak coverage and large power consumption of end nodes. Due to the shortage of NB-IoT single network in traditional application scenarios, a hybrid NB-IoT/FSK heterogeneous network architecture is proposed. With lower demodulation threshold of Frequency-Shift Keying(FSK), it can further improve the coverage of the hybrid network, reduce the end node power consumption, so as to realize more terminals’ access under the requirement of deep coverage. And then Universal Software Radio Peripheral(USRP), the software defined radio platform, is adopted to build the heterogeneous network demo system and simulate the scenario of intelligent water meter reading. By simple simulations and actual field test, this heterogeneous network is proved to be feasible and have good performance.