An electro-optic Q modulation intra-cavity frequency-doubling sub-nanosecond pulse green laser, comprising: a pump source (1), a pump coupling element (2), a polarizing beam-splitting prism (3), a laser gain medium (4), a λ/4 wave plate (5), an electro-optic switch (6), a fundamental frequency resonant cavity mirror (7), a harmonic separation lens (8), a frequency-doubling crystal (9) and a fundamental frequency/frequency-doubling resonant cavity mirror (10). By means of a short cavity structure, intra-cavity frequency-doubling, and an electro-optic Q modulation means, sub-nanosecond pulse green laser light that has high frequency-doubling efficiency is outputted, and can directly be used for occasions in which sub-nanosecond pulse green laser light is needed. By means of the intra-cavity frequency-doubling means, the advantages of a sub-nanosecond pulse output, and having a compact structure, high efficiency, stability and reliability, low costs, etc. are achieved.