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Study on tree DBH algorithm based on two-dimensional laser has engineering significance to forestry surveying. In order to solve the problem that the performance of algorithm can not be evaluated effectively when the trunk was taken as the measurement target. Five kinds of PVC tubes were scanned with laser scanning radar. Two kinds of geometric methods (tangent method and arc length method) and fitting method (Taubin), which are commonly used at present, corresponding four optimization algorithms were used to calculate diameter. The error and suitable range of the algorithm were analyzed and the performance of various algorithms was assessed. Results showed that Taubin algorithm had the highest precision, considering all samples the mean absolute error was 4.89%. It had the highest precision when measuring distance rang from 3m to 6m in which the mean absolute error was 3.62%. The errors of all calculation methods were relatively high when the pipe diameter was less than 200mm and measuring distance was less than 2m. The mean absolute error of Taubin method was 10.59%, the mean absolute error of optimized arc length method and tangent method were 14.03% and 13.47%, respectively. The accuracies of measured values of radius were greatly improved when measuring distance was further than 2m. The mean absolute error of the Taubin algorithm was reduced below 6%. Experimental results showed that the Taubin algorithm had the highest accuracy and stability in all methods, which was valuable for engineering applications.