The present invention provides a method and device for acquiring and transmitting data by an STA in a wireless local area network. The method includes: transmitting, by the STA, a PS-Poll, and receiving downlink data returned by the AP upon receipt of the PS-Poll, in a reserved time period within a current beacon interval according to a TIM contained in a beacon, after learning that the AP has the downlink data of the STA according to the received beacon, wherein the reserved time period is a period of time interval within the beacon interval; retransmitting, by the STA, the PS-Poll after the reserved time period to acquire the downlink data, if the STA can not successfully receive the downlink data within the reserved time period. Through the above solution, a mechanism is provided to address a situation that unsuccessful receiving/transmission of data can not be handled.