Inter-path interference of Multipath routing in wireless sensor networks (WSNs) is a most important problem which needs to be solved urgently.However

energy cost

concerned most in WSNs

is ignored by current interference-free schemes.The grade-based routing protocol framework MR2-GRADE (Maximally Radio-Disjoint Multipath Routing based on Grade) proposed in this paper uses hops of nodes in leading path to construct grade of nodes beyond interference zone of this path and avoids high route cost caused by broadcasting efficiently.The creation of subsequent path by grade-based local decision-making policy is affected by node distributing density of network greatly

which results in designing GRADE_GF (Grade-based Greedy Forwarding) and GRADE_RF (Grade-based Restricted Flooding).Comprehensive simulations and results indicate that compared with existed homologous routing algorithms

MR2-GRADE can decrease route cost effectively and can hold this advantage more obviously in more large-scale network.