High-Q on-chip micro-resonators has been proved to be a promising platform for Kerr soliton frequency comb generation. Si3N4 micro-resonators composed of multi-mode waveguides can achieve high quality factor and anomalous dispersion, which are necessary for soliton generation. To further reducing the threshold power for generating single soliton microcomb, a novel racetrack Si3N4 micro-resonator with Euler bends is reported, which achieved loaded Q factors of more than 5×10⁶. Compare to conventional circular bends, the sudden change in bending radius at the waveguide connection is significantly suppressed, which suppresses mode interaction and reduces propagation loss. With this novel micro-resonator, single soliton frequency combs with a repetition rate in the microwave Ka band and a bandwidth of over 20nm (corresponding to a pulse duration of 129fs) is generated with only a 47mW pump laser (33mW estimated on-chip pump power) using the auxiliary laser heating method.