Abstract: In the appraisal theory of SFL evaluation is a process whereby an attitudinal value is assigned to the target with reference to a specific criterion. Compared to the overt realisation of attitude, covert realization is still underexplored. As covert realisation can be seen as deviation from typical ways of overt realisation, with reference to the strategies for typical overt realisations we can work out the strategies for covert realisation by examining the possible ways of such deviation. These covert realisation resources include various non-attitudinal lexes, non-attributive relational processes, engagement and graduation resources and non-symbol signs, and they form a cover-overt continuum. The covert attitude will finally be manifested against a specific context, and thus contribute to the communicative purpose of attitudinal evaluation.