Ultimate bearing capacity analysis of shallow foundations has been extensively studied by geotechnical scholars. Since different hypotheses exist in the slip surface and relationship between bearing capacity factors, the value of bearing capacity factors is not same depending on the theory used. Based on the classical analytical model, a limit equilibrium method of moment equilibrium is used to deduce the bearing capacity formula of strip footing on sand, and the equations of bearing capacity factors N_q and N_γ are given. Compared to commonly used theoretical models, the equations of factors N_q and N_γ are independent thus avoid the interplay of two factors and reduce the uncertainty in calculation. In order to verify the accuracy of the equations, the calculation is compared with the theory solution of limit analysis and laboratory test results in literature. Results indicate that the N_γ values calculated by the proposed equations of different internal friction angle are closer to solution of limit analysis than other theoretical models. Furthermore, the bearing capacity calculated by equations in this paper shows good agreement with the data of laboratory test.