The invention discloses a preparation method of spherical polybutylene-1. The preparation method comprises the following steps: (1) adding alkoxy silane, an ether composite outer electron donor, a cocatalyst, a main catalyst, hydrogen and liquid-phase propylene into a tank reactor, and polymerizing at 10-25 DEG C for 5-40 minutes; (2) heating to 30-70 DEG C, carrying out secondary polymerization for 3-60 minutes, and carrying out flash evaporation to remove the residual propylene in the reactor; (3) charging hydrogen and a butylene-1 monomer into the tank reactor, and carrying out tertiary polymerization at 30-80 DEG C for 30-120 minutes; (4) introducing the butylene-1 monomer, and carrying out quaternary polymerization at 30-80 DEG C for 30-120 minutes; and (5) repeating the step (4) 2-4 times, and carrying out flash evaporation on the unreacted monomer. The method has the advantages of higher isotacticity of the prepared spherical polybutylene-1 and higher catalytic efficiency of the catalyst, and greatly shortens the crystal form transformation period.