Abstract: A joint estimation method for the peak detection & frequency offset calculation is derived which is quick, large scale, high precision, and robust.The correlation peak is detected by the double auto-correlator & robutst auto-correlating method for the fractional & integer frequency offset.The correct estimation frequency offset is got by the frequency offset status utility & the frequency offset operator.The method is simulated in the wlan receiver, in the IEEE TGN multipath channel Mode A~F, the peak detect correct rate is 100% (SNR>5) , the precision is less than 10^-2.12 (SNR>10) , the estimate scale is positive & negative 2.5 times carrier frequency unit.