偏氟乙烯聚合物及其制备方法,所述聚偏氟乙烯粉末的熔体流动质量速率为0.20~1.50 g/10 min(21.6 kg,230℃)、热分解温度为420~450℃、密度为0.2~0.6 g/mL并且相对分子质量为1.5~1.8;该聚偏氟乙烯粉末是由下列方法制得的:1)向含有引发剂和反应介质的反应容器中加入分散剂;所述分散剂是羟丙基甲基纤维素和聚乙烯醇质量比为0.5:1~1:0.5 Vinylidene fluoride polymer and a preparation method thereof. The polyvinylidene fluoride powder has a melt flow rate of 0.20 to 1.50 g / 10 min (21.6 kg, 230 ° C.), a thermal decomposition temperature of 420 to 450 ° C., a density of 0.2 to 0.6 g / mL and a relative molecular mass of 1.5 to 1.8; the polyvinylidene fluoride powder is prepared by the following method: 1) adding a dispersant to a reaction vessel containing an initiator and a reaction medium; The mass ratio of hydroxypropyl methylcellulose and polyvinyl alcohol is 0.5: 1~1: 0.5