SOURCE

<div class="loading">
  <b class="circle">
  </b>
  <b class="circle">
  </b>
  <b class="circle">
  </b>
  <b class="circle">
  </b>
  <b class="circle">
  </b>
  <b class="circle">
  </b>
  <b class="circle">
  </b>
  <b class="circle">
  </b>
</div>
<p>
  更多动画请参考：http://www.yi-jy.com/2014/06/22/css3%e4%b8%8eloading%e5%8a%a8%e7%94%bb/
</p>

.loading {
  position: relative;
  width: 40px;
  height: 40px;
  margin: 100px auto;
  border-radius: 50%;
}

.loading .circle {
  position: absolute;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  opacity: 0.6;
  background: #DD8000;
}

.loading .circle:nth-child(1) {
  left: 16px;
  top: 0;
  -webkit-animation: circleRotote05 1s 0.625s ease-out infinite;
  animation: circleRotote05 1s 0.625s ease-out infinite;
}

.loading .circle:nth-child(2) {
  left: 28px;
  top: 5px;
  -webkit-animation: circleRotote05 1s 0.75s ease-out infinite;
  animation: circleRotote05 1s 0.75s ease-out infinite;
}

.loading .circle:nth-child(3) {
  left: 34px;
  top: 17px;
  -webkit-animation: circleRotote05 1s 0.875s ease-out infinite;
  animation: circleRotote05 1s 0.875s ease-out infinite;
}

.loading .circle:nth-child(4) {
  left: 28px;
  top: 28px;
  -webkit-animation: circleRotote05 1s 0 ease-out infinite;
  animation: circleRotote05 1s 0 ease-out infinite;
}

.loading .circle:nth-child(5) {
  left: 16px;
  top: 34px;
  -webkit-animation: circleRotote05 1s 0.125s ease-out infinite;
  animation: circleRotote05 1s 0.125s ease-out infinite;
}

.loading .circle:nth-child(6) {
  left: 5px;
  top: 28px;
  -webkit-animation: circleRotote05 1s 0.25s ease-out infinite;
  animation: circleRotote05 1s 0.25s ease-out infinite;
}

.loading .circle:nth-child(7) {
  left: 0;
  top: 17px;
  -webkit-animation: circleRotote05 1s 0.375s ease-out infinite;
  animation: circleRotote05 1s 0.375s ease-out infinite;
}

.loading .circle:nth-child(8) {
  left: 5px;
  top: 5px;
  -webkit-animation: circleRotote05 1s 0.5s ease-out infinite;
  animation: circleRotote05 1s 0.5s ease-out infinite;
}

@-webkit-keyframes circleRotote05 {
  0% {
    opacity: 0.5;
    -webkit-transform: scale(1);
  }
  12.5% {
    opacity: 1;
    -webkit-transform: scale(2);
  }
  25% {
    opacity: 0.95;
    -webkit-transform: scale(1.7);
  }
  37.5% {
    opacity: 0.85;
    -webkit-transform: scale(1.4);
  }
}

@keyframes circleRotote05 {
  0% {
    opacity: 0.5;
    transform: scale(1);
  }
  12.5% {
    opacity: 1;
    transform: scale(2);
  }
  25% {
    opacity: 0.95;
    transform: scale(1.7);
  }
  37.5% {
    opacity: 0.85;
    transform: scale(1.4);
  }
}