The　interdependences　of　preparation　conditions,　magnetic　and　crystal　structures,　and　magnetocaloric　effects　(MCE)　of　the　MnFePGe-based　compounds　are　reviewed.　Based　upon　those　findings,　a　new　method　for　the　evaluation　of　the　MCE　in　these　compounds,　based　on　differential　scanning　calorimetry　(DSC),　is　proposed.　The　MnFePGe-based　compounds　are　a　group　of　magnetic　refrigerants　with　giant　magnetocaloric　effect　(GMCE),　and　as　such,　have　drawn　tremendous　attention,　especially　due　to　their　many　advantages　for　practical　applications.　Structural　evolution　and　phase　transformation　in　the　compounds　as　functions　of　temperature,　pressure,　and　magnetic　field　are　reported.　Influences　of　preparation　conditions　upon　the　homogeneity　of　the　compounds＇　chemical　composition　and　microstructure,　both　of　which　play　a　key　role　in　the　MCE　and　thermal　hysteresis　of　the　compounds,　are　introduced.　Lastly,　the　origin　of　the　＂virgin　effect＂　in　the　MnFePGe-based　compounds　is　discussed.