The solution for design model of soft landing in borehole trajectory can come down to the solution with 7-element nonlinear equations. The algorithm convergence of known numerical iterative algorithm has not been proved, and the convergence of this iterative algorithm severely depends on initial iteration value from the user. 7-element nonlinear equations are simplified to be onevariable polynomial equation by element elimination and simplification; and based on which, a new algorithm for design model of soft landing was developed. Theoretical analysis and practical calculation examples show that the new algorithm is mainly for the calculation of nonnegative real roots of polynomial equation, and calculation of functional relationship between other unknown number and real root is very less. The new algorithm overcomes the dependence on the initial value and probable iterative process divergence, and can get the solutions at the same time when there are several design model solutions.