A erbium-doped fiber ring laser, which utilizes a single-stage polarization-independent acousto-optic tunable filter by use of quasi-collinear coupling as the tuning component, is proposed and a continuously tunable lasing wavelength is realized. The filtering principle of the polarization-independent quasi-collinear filter is introduced briefly, and then the compensation of frequency-shift is analyzed. The experimental results are that the output power of the laser pumped at 13 mW is measured to be 322 μW at a lasing wavelength of 1550 nm, the threshold pump power is 7.65 mW, and the slope efficiency is 6.02%; the tuning range of 38 nm, starting from 1524.7 nm ending at 1562.4 nm, is observed.