Abstract: Electron optical injection is an efficient all-optical injection scheme in laser wakefield accelerations. However, low-charge and large emittance electron beam is still not suitable for many practical applications. This paper presents a novel injection scheme by colliding a tightly focused super-Gaussian laser with a Gaussian pump laser. It is found that the emittance of electron beam becomes almost an order of magnitude lower than that of all-Gaussian case, while the charge of electron bunch is conserved. It is also found that the electron emittance is mainly attributed to off-axis injected electrons by a Hamiltonian model. This unique ability will pave the way towards the generation of high-quality electron beams and extend the applications of laser-plasma accelerators.