The invention discloses a broadband wireless transmission method assisted by a distributed intelligent reflecting surface, and is suitable for the field of wireless communication. The method comprisesthe steps: evaluating the influence of each system parameter according to the closed expression of the downlink traversal rate of a large-scale multi-antenna millimeter wave broadband orthogonal frequency division multiplexing system, and guiding the hardware erection of an IRS array plane; in broadband system transmission, by a user, sending a pilot signal, estimating a reflection channel of each IRS, matching the strongest time domain tap to reduce complexity, channel estimation overhead and feedback quantity, and using an IRS phase shift matrix to match a IRS-to-user channel, a base station-to-IRS channel, and a base station-to-user channel to maximize downlink rate. An IRS transmission method with low channel estimation overhead, low feedback quantity and low complexity is provided, and an IRS phase shift matrix is used for matching the IRS-to-user channel, the base station-to-IRS channel and the base station-to-user channel so as to maximize the downlink rate.