A long-term transient simulation is conducted using the Community Climate System Model version 3 and the orbital acceleration technique to analyze the impact of insolation change caused by the Earth's orbital forcing on precipitation in the monsoonal East Asia (EA) and arid central Asia (CA) over the past 150 ka. Our results show that annual precipitation in both EA and CA has strong signals of the 20 ka precessional cycles and varies in phase with the Northern Hemisphere (NH) summer insolation. Similar characteristics can also be observed from previously published oxygen isotope records of stalagmites near EA and CA. Composite analyses based on seven precessional cycles suggest that the increase (decrease) in the NH summer (winter) insolation enhances EA (CA) summer (winter) precipitation by modulation of the Asian monsoon (westerly) circulation in summer (winter). When the precession-induced NH summer insolation increases, the Asian summer monsoon circulation is enhanced and EA precipitation increases significantly. Meanwhile, the increase in the summer insolation at the precessional scale is accompanied by a decrease in the winter insolation, which causes dramatic cooling of the troposphere in the lower latitudes. Consequently, the CA winter precipitation increases due to the changes in the temperature gradient and the westerly circulation. Therefore, the responses of the Asian monsoon and westerly circulation to summer and winter insolation variations induced by the precessional cycles determine precipitation in the respective rainy seasons and are the primary cause leading to the synchronous variation patterns of annual precipitation in EA and CA at the orbital scale.