A method for determining a time offset, wherein the method comprises: obtaining, by a device at a head end, a time-domain signal, wherein the time-domain signal is obtained based on a signal received by the device at the head end by multiplication in the frequency domain of the received signal and a reference signal, followed by conversion into the time domain, and the signal received by the device at the head end comprises a ranging signal sent by a terminal; and determining, by the device at the head end, a time offset based on values of peak-to-average ratios of a preset quantity of symbols starting from a q th symbol in the time-domain signal, wherein the time offset is a difference between a first time point and a second time point, the first time point is a time point at which the ranging signal sent by the terminal arrives at the device at the head end, the second time point is a preset reference-point time point, and a peak-to-average ratio of the q th symbol is greater than a preset threshold, wherein q is any integer greater than or equal to 1, characterized in that the determining, by the device at the head end, a time offset based on values of peak-to-average ratios of a preset quantity of symbols starting from a q th symbol comprises: when there are a plurality of symbols whose peak-to-average ratios are greater than the preset threshold in the preset quantity of symbols, and Pm - Pn > Pn - Threshold, determining, by the device at the head end, the time offset according to a second formula, wherein the second formula is: TA = m − 2 ∗ Nsymb + Lm − 1, wherein the preset threshold is Threshold, Pm is the largest value in the peak-to-average ratios of the preset quantity of symbols, Pn is the second largest value in the peak-to-average ratios of the preset quantity of symbols, TA indicates the time offset, Nsymb indicates duration occupied by any symbol in the signal received by the device at the head end, Lm indicates a difference between a sampling-point time point corresponding to a peak of an m th symbol and a start sampling-point time point of the m th symbol, a peak-to-average ratio of the m th symbol is Pm, a symbol whose peak-to-average ratio is Pn is an n th symbol, and m and n are any integers greater than or equal to q. obtaining, by a device at a head end, a time-domain signal, wherein the time-domain signal is obtained based on a signal received by the device at the head end by multiplication in the frequency domain of the received signal and a reference signal, followed by conversion into the time domain, and the signal received by the device at the head end comprises a ranging signal sent by a terminal; and determining, by the device at the head end, a time offset based on values of peak-to-average ratios of a preset quantity of symbols starting from a q th symbol in the time-domain signal, wherein the time offset is a difference between a first time point and a second time point, the first time point is a time point at which the ranging signal sent by the terminal arrives at the device at the head end, the second time point is a preset reference-point time point, and a peak-to-average ratio of the q th symbol is greater than a preset threshold, wherein q is any integer greater than or equal to 1, characterized in that the determining, by the device at the head end, a time offset based on values of peak-to-average ratios of a preset quantity of symbols starting from a q th symbol comprises: when there are a plurality of symbols whose peak-to-average ratios are greater than the preset threshold in the preset quantity of symbols, and Pm - Pn > Pn - Threshold, determining, by the device at the head end, the time offset according to a second formula, wherein the second formula is: TA = m − 2 ∗ Nsymb + Lm − 1, wherein the preset threshold is Threshold, Pm is the largest value in the peak-to-average ratios of the preset quantity of symbols, Pn is the second largest value in the peak-to-average ratios of the preset quantity of symbols, TA indicates the time offset, Nsymb indicates duration occupied by any symbol in the signal received by the device at the head end, Lm indicates a difference between a sampling-point time point corresponding to a peak of an m th symbol and a start sampling-point time point of the m th symbol, a peak-to-average ratio of the m th symbol is Pm, a symbol whose peak-to-average ratio is Pn is an n th symbol, and m and n are any integers greater than or equal to q.