Pendulous integrating gyro-accelerometer（ PIGA） generally operates in low-frequency and high-overload environment

and its quadratic error is very small. Considering the small input acceleration signal in gravity field testing

the non-linear error is too small to be measured accurately. A test method for the separation of PIGA nonlinear quadratic term on the low-frequency linear vibrator is presented

which is used to simulate the actual high overload environment. The index of model correlation R~2 approach 1 and residual error σ is 3. 935 × 10

-4

non-linear regression analysis theory are used to test calibrated model. Test results show that this method can effectively separate t

he quadratic term coefficients of PICA. The model has good fitting effect and high identification precision.