For the infrared band near 1 550 nm, a transmissive beam deflector based on a dielectric metasurface is proposed. This deflector can achieve a large deflection angle together with a broadband spectrum and high efficiency. The structural design of the deflector is optimized according to the generalized Snells law. It comprises amorphous silicon nanopillars with trapezoidal cross sections that are arranged periodically on a quartz glass substrate. The continuous phase gradient formed by the unique trapezoidal nanopillars in the proposed structure provides superior deflection characteristics compared with those provided by the discrete phase gradient formed by the discrete nanopillars utilized in traditional metasurfaces. The performance of the proposed device is simulated and analyzed with respect to efficiency, deflection angle, wavelength dependence, and incident angle dependence using the finite-difference time-domain method. The performance of this device is tested after its fabrication via processes such as electron beam lithography. The simulations indicate that this deflector realizes a deflection angle as large as 42.8° at 1 550 nm, as well as a transmissivity of 84%, a deflection efficiency of 80%, and an allowance of incident angle between -10° and 5°. Moreover, the deflector exhibits impressive deflection characteristics for wavelengths ranging from 1 350—1 650 nm, with an average transmissivity exceeding 87% and an average deflection efficiency of 81%. Experimental test results show that, at the wavelength of 1 550 nm, the beam deflection angle is nearly 41°, the device transmissivity is approximately 76%, and approximately 35% of the incident light is deflected to the target angle. The proposed device represents a new approach for the design of near-infrared metasurface devices and has application potential in numerous fields.