Abstract: In the offloading problem of mobile edge computing task, the traditional offloading algorithm only considers the computing resources of mobile devices and edge servers, and has some limitations in resource utilization and system efficiency. this paper proposes an edge-cloud weighted serial task offloading algorithm based on rainbowDQN (ECWS-RDQN) based on the RainbowDQN algorithm, considering the factors of delay, energy consumption cost and service quality assurance. This algorithm realizes the serial task dynamic assignment processing of network edge and cloud collaboration through the weight to provide approximately optimal task assignment offloading strategies for different user device applications. Experiments show that the ECWS-RDQN algorithm has better system efficiency than the traditional schemes and improves the service quality of the applications.