A multiple input multiple output (MIMO) antenna system, a signal transmission method, a signal transmission apparatus and a computer program product for the MIMO antenna system are provided. The signal transmission method comprises the following steps of transmitting a signal with a first signal transmission mode and a first transmission power via a signal transmission channel; receiving a signal to noise ratio (SNR) of the signal; receiving an interference value of the signal transmission channel; obtaining a power weight value according to the interference value; determining a system threshold of the signal transmission channel to the SNR of the signal; determining a second signal transmission mode of the signal transmission channel based on the system threshold; and determining a second transmission power of the signal transmission channel according to the power weight value.