We consider a hybrid two-tiered sensor network consisting of regular resource-limited sensor nodes and powerful master nodes with abundant resources. In the architecture, master nodes take charge of storing data collected by sensor nodes and processing queries from the base station. Due to the important role of master nodes, they might easily become the target for the adversary to compromise in an untrusted or hostile circumstance. A compromised master node may leak sensitive data in its storage to the adversary, which breaches the data privacy. This paper proposes EMQP, a novel and energy-efficient privacy-preserving MAX/MIN query protocol which is capable of preventing adversaries from obtaining sensitive data collected by sensor nodes. To preserve privacy, the 0-1 encoding verification, keyed-hash message authentication coding, and symmetric encryption are applied to achieve the secret comparison of data items without knowing their real values. On the basis of secret comparison mechanism, the data submission and query processing protocols are proposed to describe the details of EMQP. And the analyses on privacy protection and energy consumption are also given. Moreover, a hash-based optimization method is presented to save more energy of the resource-limited sensor nodes. The simulation result shows that EMQP is more efficient than the current work in energy consumption.