The present invention relates to a multiple-input-multiple-output (MIMO) wireless transmission system and a transmission method thereof. A wireless transmitting system thereof receives encoded data via a first processing unit, which processes the encoded data and outputs the encoded data to a plurality of modulation units for modulating the encoded data to produce a plurality of modulated data. A plurality of first conversion units converts the plurality of modulated data to a plurality of transmitting signals. A plurality of radio-frequency (RF) circuits receives the plurality of transmitting signals and transmits RF signals according to the frequency-hopping sequence of a piconet. A plurality of receiving processing units of a wireless receiving system according to the present invention receives the RF signals, respectively, according to the frequency-hopping sequence of the piconet and transmits to a plurality of second conversion units for converting the RF signals to received data. A switching circuit switches the received data according to the frequency-hopping sequence of the piconet. A plurality of demodulation units demodulates the switched received data to produce demodulated data. A second processing unit received the demodulated data, and processes the demodulated data to output demodulated data. A decoding unit decodes the demodulated data output by the second processing unit to produce output data.