According to the theory of noncommutative quantum gravity[1][2], we calculate the self-interaction of gravitons in momentum space. It shows that the self-interaction of gravitons makes the gravitational field deviate from the inverse square law. By calculating the metric, it can be ob- tained that the stronger the gravitational source, the stronger the energy- momentum of the excited gravitons, and the stronger the gravitational effect produced by the self-interaction of gravitons. Maybe be it can be used to explain dark matter and the Pioneer anomaly.