A new theory shows that the gravitational constant may be variable with changes in space. Since the earth orbits the sun, there are perihelion and aphelion, which causes the constant changes of the gravitational constant measured by the earth at different orbital positions. This change in the gravitational constant directly causes a change in the gravitational force on the earth's matter. If the earth's gravitational constant changes, it will lead to changes in the potential energy of the entire atmosphere, which in turn will cause changes in kinetic energy of air. The formation of tropical storms is more sensitive to changes in atmospheric energy. If there is enough energy change, under other conditions suitable, it may cause a rapid increase or decrease in the frequency of tropical storms. This article compares the existing tropical storms on the earth and finds that after the earth begins to move out of the aphelion (in July), the earth’s gravitational constant begins to increase gradually. This leads to a decrease in the potential energy of the earth's atmosphere, causing a gradual increase in kinetic energy of air. This increase in kinetic energy can easily lead to the instability of the sea level atmosphere, and then more tropical storms. The earth's orbit begins to deviate from the perihelion (January), and the earth's gravitational constant begins to gradually decrease, which leads to an increase in the potential energy of the earth's atmosphere, which in turn leads to a gradual decrease in the kinetic energy of air. The reduction of kinetic energy of air also means that more atmospheric disturbance energy can be absorbed, thereby reducing the frequency of tropical storms. This trend is in line with the global tropical storm record for a long time in the past. It is a good explanation why there are many tropical storms in August and September, but there are very few tropical storms in April and May.