The correlation between the magnetocaloric effect and magnetotransport property was investigated in Ni43Co7Mn39-xCrxSn11 Heusler alloys. The asymmetric isothermal-magnetoresistance around the phase transformation temperature was observed, from which a parameter γ, determined as the ratio of the asymmetric magnetoresistance to the temperature coefficient of resistance, is proposed. According to Maxwell's equation, the parameter γ is analyzed to be equivalent to the transformation temperature change induced by a magnetic field in martensitic transformation. This finding is confirmed by experimental results. In addition, the γ values can be used to estimate the magnetic entropy change of the martensitic transformation directly without measuring the comprehensive temperature dependence of magnetization curves.