According to Henry's law, the solubility of the gas in a solution is directly proportional to the pressure of that gas which is above the surface solution.
When pressure increases, the gas molecules forcefully come into the solution, due to this applied pressure is relieved. Thus, there is a decrease in the number of gas molecules. The number of gas molecules in the solution will increase. As there is an increase in the pressure of a gas, then there is an increase in collision frequency and so that the solubility increases, and if the pressure decreases the solubility also decreases.