According to the multiple phases during the ground manoeuvres, different loading cases were analyzed and the relevant breakdown models as well as the derivation method for the landing gear loading spectrum were provided. In order to do research on the typical structure of nose undercarriage and the general loading actions, the load model and the mathematic model were built based on the general nose landing gear structure. Critical load case picked from the loading spectrum was studied and real reasonable aircraft structure parameters were introduced in the calculation. The results indicate the method of combining the loading spectrum and the mathematic model to obtain the main joint loads was feasible which could be the support for the later fatigue life estimation. This paper provides the methods and theoretical support for loading spectrum development and the loading analysis of undercarriages.