Who are the manufacturers of RFID readers?

This depends on whether to use low frequency, high frequency or ultra-high frequency. Generally speaking, it is as follows

Tag chip:

NXP, Infineon, Inside, Atmel, Ti, Philips, Intermac, Alien, Matrics, SGS, EM.

Imported reading and writing equipment:

Impinj, Alien, Xunbao, ThingMagic, CSL, Intermec, Siemens, etc.

The more mature ones in China are Wangyuan Valley (UHF) and Shanghai Hao Bin (both HF and UHF).