The offset and nonlinearity of the readout circuit of the indirect time of flight (I-ToF) image sensor have a crucial impact on the ranging accuracy. This paper presents a 320×240 I-ToF image sensor with 5.6μm×5.6μm 2-Tap pixel in 110nm process, in which, the readout channel offset cancellation and nonlinearity suppression techniques are proposed to achieve high-precision detection. The measured relative precision is 1% at a 5m target distance and non-linearity is below 1.02%. The chip also integrates LVDS and I2C interface for the data transmission and Laser control.