An all-digital adaptive background algorithm for calibrating the channel mismatch error of the time-interleaved analog-to-digital converter (TIADC) was proposed. The algorithm used the Walsh function to modulate and generate the spurious signal only from the output of the TIADC, which could reconstruct the mismatch error and adaptively subtract three mismatch errors from the TIADC output. The advantage of the proposed technique was that it only needed to know the output signal of measurement and the number of TIADC channels without any other information including the reference channel. At the same time, aimed at the problem that the algorithm (most modulation algorithms) was unable to calibrate special frequency points, a frequency judgment module was designed in this paper, and extra spurs of special frequency points was eliminated by a set of low-pass filters and band-pass filter, which overcame the limitation of the algorithm. Simulation results showed that the proposed technology could effectively eliminate the channel mismatch errors, thereby greatly improving the performance of the TIADC system.