An adaptive serial general-purpose input output (ASGPIO) interface and a signal receiver thereof suitable for a secure control module (SCM) are provided. The ASGPIO interface includes a signal transmitter. The signal transmitter includes a first data buffer, a comparator, and an encoder. The first data buffer receives transmitted data and provides previously transmitted data. The comparator receives currently transmitted data and receives the previously transmitted data. In a first mode, the comparator compares the previously transmitted data with the currently transmitted data to generate a data variation information. The encoder, in the first mode, generates at least one index value and a corresponding instruction signal according to the data variation information. The signal transmitter sends the at least one index value as a serial signal and the instruction signal to a signal receiver.