The invention brings forward a 3D MIMI (Massive Multiple Input Multiple Output) transmission method and device. In the first step, UE sends a first CSI (Channel Status Indicator), and a reference resource of the first CSI is a first RS (Reference Signal). In the second step, the UE sends a second CSI, and a reference resource of the second CSI is a second RS. The first CSI includes a first PMI (Precoding Matrix Indicator), and the first RS is a broadband RS. The second CSI includes at least one of a second PMI and a second CQI (Channel Quality Indicator), the second RS is a narrowband RS, and the first RS and the second RS are sent by the same cell. According to the scheme, the UE estimates the second CSI according to a narrowband measurement RS sent by precoding, the estimation precision of the second CSI is improved, and the air interface cost brought by measuring of the RS is reduced. Moreover, a conventional LTE design is utilized as much as possible, and compatibility with a conventional system is kept to the maximum.