Monolayer and multilayer graphene films have been grown on a Cu substrate by chemical vapor deposition (CVD) and then transferred onto a SiO2/Si substrate using polymethyl methacrylate (PMMA) to fabricate an ultrasensitive graphene-based strain gauge sensor. The graphene films were patterned using a CO2 laser beam. The sensitivity and temperature dependence of the gauge factor (GF) of the fabricated sensors were examined at different applied strains and operating temperatures up to 0.05% and 75 ℃, respectively. The fabricated gauges based on monolayer and multilayer graphene films show stable GFs of 255 and 104 within the applied temperature range, respectively. The patterning technique provides an interesting, low-cost, fast, and high-throughput process to realize scalable microfabrication for highly sensitive strain sensors with good temperature stability based on graphene piezoresistivity. A theoretical simulation of the GF of monolayer graphene has also been carried out on the basis of first-principles calculation. Simulation results follow the measured GFs in our experiment and other references.