This paper presents background offset and gain calibration for time-interleaved analog-to-digital converter (TIADC). The calibration technique depends on detecting the offset and the amplitude of a calibration signal. The detection is based on a simple algorithm performed in the digital part. A digital sinusoidal wave is needed to implement the calibration technique. The calibration technique behaviors are theoretically analysed and verified by simulations. A 12-bit, 4-channel, 800 MS/s TIADC is used as an example.