Abstract: A closed circle DNA computing model and its bio-chemistry experiments are introduced.The flexibility of a closed circle DNA molecule structure is brought forward,which includes the controllabitity of DNA chains in length and mutual conversion among the DNA molecules.For the 0-1 planning problem of nonnegative integer coefficients,a closed circle DNA algorithm is put forward.In the closed circle DNA algorithm,first the five groups of DNA encoding are encoded according to variable’s 0 or 1 values,its coefficients and its detecting mark.All possible solutions are synthesized.Then all feasible solutions are filtered out using the insert experiment,electrophoresis experiment and delete experiment.All optimization solutions are filtered out using the same method.Finally all optimization solutions are found using a detect experiment.The correctness of the algorithm is proved,and the complexity of the algorithm is discussed.And the feasibility of the DNA algorithm is explained by an example.The closed circle DNA algorithm is improved so as to solve the 0-1 planning problem of the real coefficient including negative numbers.