The invention discloses a method for measuring two-dimensional stress at a weld joint by using a 
Barkhausen effect and a detection instrument. A ferrite 
magnetic core and a 
magnetic core of a Barkhausen measuring probe are directly contacted with the surface of the weld joint of the test piece, so that the X-direction 
tangential stress and the Y-direction axial stress of the weld joint of the test piece are calibrated; the Barkhausen measuring probe is used for collecting excitation signals and detecting Barkhausen signals, stress 
signal amplitude waveforms are obtained, and 
signal amplitude noise is obtained according to the waveforms; a Barkhausen 
noise signal amplitude is extracted from a signal detected by the Barkhausen measuring probe, the Barkhausen 
noise signal amplitude continuously changes along with the tension and 
pressure stress values to form a tension and pressure fitting curve, and the tension and pressure fitting curve serves as a 
calibration result of the relation between the Barkhausen 
noise signal amplitude and the continuous tension and 
pressure stress; and finally, a Barkhausen noise signal, the 
residual stress sigma1 in the vertical direction, the 
residual stress sigma2 in the parallel direction and the quantitative relation of the included angle theta between the main stress direction and the 
magnetic field direction are obtained, and the two-dimensional 
residual stress of the 
welding area is directly detected.