An opportunistic spectrum access method based on Markov chain and CSMA includes that the access predication statistical module method of the Markov chain is combined with the CSMA access protocol to adopt different access modes according to different induction areas, before the user access is recognized, the spectrum detection is carried out according to spectrum induction method, and the first and second dual thresholds Lambda 1 and Lambda 2 of the interference temperature of the master user, the judgment area whether the master user exists is divided according to the two thresholds, when the interference temperature value is less than the Lambda 1, the user is recognized and accessed directly; when the interference temperature value is more than the Lambda 2, the CSMA access mode is adopted for back-off access; when the interference temperature is between the Lambda 1 and Lambda 2, a Markov chain access predication statistical module with the master user as the priority is built in queuing and non-queuing modes, and the Markov chain module is adopted to describe the opportunistic spectrum access. During access process, the first and second interference temperature thresholds are regulated dynamically to realize the maximization of the whole network throughput.