The invention discloses an MEMS piezoresistance type two-axis acceleration sensor chip and a preparing method thereof. The MEMS piezoresistance type two-axis acceleration sensor chip comprises four sets of same sub-structures. The four sub-structures are uniformly distributed at the periphery of a fixed island. The fixed island is connected with a mass block through an inner supporting beam. The mass block is connected with an outer frame through an outer supporting beam. Sensitive beams are symmetrically distributed at two sides of the outer supporting beam. One end of the sensitive beam is connected with one end of the mass block, and the other end of the sensitive beam is connected with the outer frame. The two sub-structures which face each other relative to the fixed island form a set, thereby forming a whole working structure for measuring one acceleration direction, thereby respectively measuring the accelerations in an X-axis and a Y-axis. The two sensitive beams of each sub-structure are respectively provided with a pressure-sensitive resistor and are connected with a pad through metal leads, thereby forming a semi-open-ring Wheatstone full-bridge circuit. The sensor chipcan realize separated measurement of the accelerations below 200g in two axes. The natural frequency of the MEMS piezoresistance type two-axis acceleration sensor reaches above 20kHz, and the sensitivity is higher than 0.5mB/g/3V. Furthermore the MEMS piezoresistance type two-axis acceleration sensor chip has relatively high resonant frequency and high sensitivity.