Objective：To investigate the relation between nitrite solutions with different concentrations and methemoglobin formation rates，to invent a rapid，safe and economical detection card for blood methemoglobin concentration in human and to provide references for forensic science and clinical work. Methods：According to the dose-effect equation between nitrite solutions with different concen－trations and methemoglobin formation rate，nitrite solutions with different concentrations were obtained for generating methemoglobin blood samples with different concentrations（10%-80%）. Then，blood samples from healthy donors and methemoglobin blood samples with different concentrations were dropped on the blood collection cards. The values of red，green，blue（RGB） were acquired，and different methemoglobin color-pieces were generated. Finally，the rapid detection card was successfully fabricated. Results：Nitrite solution with different concentrations and methemoglobin formation rates was in linear correlation.With the increasing of concentration of methemoglobin in the blood sample，the color of the detection card became more and more dark. Conclusion：This detection card is rapid，safe and economical for methemoglobin concentration detection. Therefore，it might be widely applied in the future.