Abstract: An insert device TOK has been built up and mounted on the storage ring of NSRL. The magnetic field distribution of TOK is additionally measured, and the harmonic components of magnetic field distribution in strength were analysed. And the integral field distribution is measured, and the investigation of the origin of the integral variation is taken. The uniformity of the transvers distribution of the field is checked to provide the experimental data for the coherent harmonic generation and FEL investigation in the future. Finally, numerical simulation on spontaneouse radiation from TOK is taken with the measured data, and the result illustrates that the TOK is taken with the measured data, and the result illustrates that the TOK can satisfy the experimental requirement.