The present invention provides a projection prime lens including first lens group, a second lens group, and a third lens group arranged in sequence along an optical axis from a screen side to a light modulator side. The first lens group has negative refractive power and includes a first lens with negative refractive power and a second lens with negative refractive power. The second lens group has positive refractive power and includes a third lens with positive refractive power and a fourth lens with positive refractive power The third lens group has positive refractive power and includes a fifth lens with negative refractive power, a sixth lens with positive refractive power, and a seventh lens with positive refractive power. Therefore, the projection prime lens of the present invention has a small size and a good image quality.