The invention discloses a preparation method of germane, comprising dripping tetrahydrofuran solution of germanium tetrachloride into sodium hydroxide solution of sodium borohydride to react, and preparing the germane; wherein the molar ratio between the germanium tetrachloride and the sodium borohydride is 1:1-10. The reaction is carried out according to the equation: GeCl4+NaBH4+3NaOH=GeH4+B(OH)3+4NaCl. The method is simple in technique and lower in cost; and the prepared germane has high yield and less impurity content, and is easy to purify.