This paper presents a time-domain CMOS temperature sensor with linearity optimization. We employ a bipolar junction transistor (BJT)-based frontend together with an on-chip temperature-compensated gated ring oscillator (GRO) with intrinsic first-order noise shaping to achieve both high linearity and accuracy. This work also systemically optimizes the nonlinearity introduced by: 1) the curvature of VBE;2) the voltageto-Time conversion; and 3) the quantization error. Implemented in a standard 0.1\mathrm{S}-\mu \mathrm{m} CMOS process, this work demonstrates an inaccuracy of \pm 0.35{\circ}\mathrm{C} and a conversion time of 0.165ms over a wide temperature range from-40 to 125{\circ}\mathrm{C}, featuring a favorable accuracy-and resolution-FOM of 0.64nJ% 2 and 17.4\mathrm{p}\mathrm{J}{\circ}\mathrm{C}{2}, respectively.