Embodiments of the present invention provide a data transmission apparatus and method. The data transmission apparatus includes: a processor, configured to, record a link quality indication value corresponding to received data and add 1 to a count value, if the data is received within a preset period of time; if it is learned by comparison that the count value is not less than a quantity N of pieces of data allowed to be transmitted in a current period, calculate an average value of link quality indication values; and compare the average value with a threshold to determine a quantity of pieces of data allowed to be transmitted in a next period The apparatus also includes a transceiver, configured to reply with a periodicity acknowledgment frame that carries the quantity of pieces of data allowed to be transmitted in the next period.