The invention provides a joint resource optimization method based on an underwater acoustic OFDM-NOMA (Orthogonal Frequency Division Multiplexing-Non-Orthogonal Multiple Access) system downlink and isused for solving a problem that in the prior art, no underwater non-orthogonal multiple access network resource allocation mechanism with high feasibility exists. An underwater acoustic wireless communication system based on OFDM-NOMA is established. A base station (BS) and K anchor nodes are deployed in the system. A channel information state of each anchor node is known. A constraint conditionis given. The constraint condition comprises a total transmitting power Pt of the base station and a constraint of subcarrier allocation number. A system rate sum is taken an objective function. In order to solve a joint resource optimization problem, the provided optimization problem is finished step by step. Subcarrier allocation is carried out through adoption of a greedy algorithm with relatively low algorithm complexity, so a system subcarrier allocation optimization objective is satisfied. For power allocation, an optimization objective is converted from a transmitting power to a communication rate, a power allocation model is converted into a strict convex optimization problem, and an optimum value is solved through adoption of a GP (Geometric Programming) algorithm. The method is scientific and reasonable, is low in algorithm complexity and is applicable to an underwater bad communication environment.