需要最外面div加隐藏属性

<div class="home_wrap">.....</div>

.home_wrap {
		overflow: hidden;
		width: 100%;
		min-height: 100vh;
		background: url(../images/new/index-bg.png) center top no-repeat;
		background-size: contain;
	}

@keyframes bounce {
	  0%, 20%, 50%, 80%, 100% {
		-webkit-transform: translateY(0);
		-ms-transform: translateY(0);
		transform: translateY(0);
	  }

	  40% {
		-webkit-transform: translateY(-15px);
		-ms-transform: translateY(-15px);
		transform: translateY(-15px);
	  }

	  60% {
		-webkit-transform: translateY(-5px);
		-ms-transform: translateY(-5px);
		transform: translateY(-5px);
	  }
	}