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A method of 3-D tolerance modeling and analysis for operation removal model was proposed based on operation feature recognition. The roughcast was considered as the assembly of part model and operation removal models. Small displacement torsor (SDT) theory was used to describe design and process tolerances while the changeable constrains of tolerance torsors were calculated. The tolerance network graph of the operation removal models was constructed and the tolerance propagation mechanism in the tolerance network was discussed. Then the process tolerance stack-up models were achieved, which was the basis of process tolerance allocation. Finally, a case was analyzed to verify the validity of the proposed theory. The process tolerance allocating method based on the proposed theory was mentioned briefly.