Optical scanner is often used to scan through certain angel at certain frequency; but a galvanometer optical scanner can scan at higher frequency with smaller angle. This paper uses the second order of differential equation for damped oscillation describing the dynamic characteristic of galvanometer, analyzing the transfer function of galvanometer scanner under a harmonic driver force. The solution indicates that the scanning under harmonic drive is still a harmonic oscillation at the same frequency. The reciprocal square of scanning angle can be expressed as a function of frequency square. Measured the scanning angle under a certain frequency, accordingly providing a reference to achieve high frequency scanning. Basing on the above result of analysis and experiment, bring forward a design idea of smaller scanning reflector to fit smaller angle scanning, and carrying on experiment to prove the feasibility.