Next generation of Geometrical Product Specifications (GPS) is the foundation of the technology standards and metrology specifications of mechanical and electric products. GPS estimation of measurement uncertainty can improve the reliability of the verification result. In the indirect measurement, the transfer characteristic is very complex. So, it is very difficult to estimate the uncertainty in the indirect measurements according to the transfer formula given by GUM. For the indirect measuring of an inside cone angle, the mathematical relation between the measurand and measurement results is established firstly. Then Monte Carlo method was adopted to conduct the sampling and synthesis of measurement uncertainty contributors. At last, the measurement method was evaluated and improved according to Procedure for Uncertainty Management. Experimental result shows that Monte Carlo Simulation method has a good application foreground in the uncertainty estimation and measurement program design.