We report an integrated Thermoresistive Micro Calorimetric Flow (TMCF) sensor with the detection limit towards $\mu\mathrm{m}/\mathrm{s}$ level by using proprietary InvenSense CMOS MEMS technology. The TMCF sensor shows a prominent normalized sensitivity of $533\mu \mathrm{V}/(\mathrm{m}/\mathrm{s})/\mathrm{mW}$ for N2 flow (−1.29m/s∼1.29m/s). With the very low flow testing in the mixed convection regime $(Gr/Re^{2} > 1)$, the TMCF sensor shows a good resolution of less than 3.2mm/s and Minimum Detectable Flow Velocity (MDFV) of less than 1.6mm/s (2% error). Moreover, the intrinsic MDFV and resolution of the TMCF sensor to the noise level at the zero flow is determined as good as $30\mu \mathrm{m}/\mathrm{s}$ and $60\mu \mathrm{m}/\mathrm{s}$, respectively. Therefore, this proposed TMCF sensor will be a promising flow device for ultra-low fluid flow measurements in micro/nanofluidics.