It isn't, it has a Socialist Market Economy. Marx and Engels repeatedly stated that Private Property cannot be abolished all at once in lower-stage Communism (which modern Marxists call Socialism). The economy of China is over 50% publicly owned and centrally planned, and there is a cooperative sector as well, meaning the Private Sector is a minority. On top of this, the Private Sector is still centrally planned.

The PRC employs a "birdcage model," where competition in the markets eventually leads to monopolization into large syndicates, which the CPC then folds into the public sector steadily as it increases control by degree.

This is exactly why I linked you the article Socialism Developed China, Not Capitalism. If you aren't going to read Marx and Engels, and you aren't going to study Historical Materialism, surely you can read a 20 minute article, right?

I'll leave you with an excerpt from The Principles of Communism:

Will it be possible for private property to be abolished at one stroke?

No, no more than existing forces of production can at one stroke be multiplied to the extent necessary for the creation of a communal society.

In all probability, the proletarian revolution will transform existing society gradually and will be able to abolish private property only when the means of production are available in sufficient quantity.

I bolded the section where Mao made an error in judgement and socialized the economy dramatically before the productive forces were developed enough.