A method and apparatus for precoding matrix indicator feedback reduce a quantity of bits in the feedback. In the method, a terminal device receive a reference signal from a base station, determines a precoding matrix W in a precoding matrix set corresponding to a rank indication. W satisfies W=W1×W2×W3, W1, W2 and W3 and matrices and respectively corresponding to a first, second and third precoding matrix indicator. None of W1, W2, and W3 is an identity matrix, and the 2M columns in W1 comprise every column in W1×W2. The terminal device transmits the rank indication, the first precoding matrix indicator, the second precoding matrix indicator, and the third precoding matrix indicator to the base station. Therefore, a quantity of to-be-selected vectors is reduced by using a first-stage feedback and a second-stage feedback, thereby reducing calculation complexity of third-stage feedback, and reducing a quantity of bits in the third-stage feedback.