In this paper, we discuss the effects of heterogeneous neuron arrangement on the frequency synchronization of a ring-coupled FitzHugh-Nagumo neuronal network. The obtained numerical results reveal that the threshold of coupling strength for frequency synchronization may be different for different arrangements of the heterogeneous neurons on a ring. On average, the closer to each other the neurons which are less heterogeneous on a ring, the larger the critical coupling strength needed for neuronal network to achieve frequency synchronization is; the closer to each other the neurons which are more heterogeneous, the smaller the critical coupling strength needed for neuronal network to achieve frequency synchronization is. Furthermore, we give the underlined mechanism for this phenomenon by analyzing the process of frequency synchronization.