For estimating attitude of unresolved targets, such as high earth orbit targets and micro-nano satellites, according to the analysis of correlational research at home and abroad, the main attitude estimation methods based on photometric data are comprehensively summarized. Then both the advantages and disadvantages of these methods are analyzed. The attitude inversion method based on the nonlinear filter has high precision and near-realtime efficiency in the cases of steady state and maneuvering condition, and it is the dominant method in the future. On this basis, the key issuses of attitude inversion based on nonlinear filter are studied, such as shape inversion, selection of bidirectional reflectance distribution function models and its parameters, and the nonlinear filtering algorithm is discussed.