This is stupid thought. To reduce population, it can only slow down everything. At first, it will produce a aging country. China must let the population maintain at the level where young people is in majority.
Be careful not to just measure the population, watch out for the birth rate change. When a population gets old, birth rate drops a lot, that causes population to shrink further.
Balance the birth rate with the death rate to keep the population!
Birth rate depends on the population in age 20's to 40's. Death rate is mainly determined by the people over 50's.