使用CSS设置边框动画

{
  background: none;
  border: 0;
  box-sizing: border-box;
  box-shadow: inset 0 0 0 2px #f45e61;
  color: #f45e61;
  font-size: inherit;
  font-weight: 700;
  margin: 1em;
  padding: 1em 2em;
  text-align: center;
  text-transform: capitalize;
  vertical-align: middle;
}
.draw {
  overflow: hidden;
  position: relative;
}
.draw::before, .draw::after {
  content: '';
  box-sizing: border-box;
  position: absolute;
  border: 2px solid transparent;
  width: 0;
  height: 0;
}
.draw::before {
  top: 0;
  left: 0;
  border-top-color: #60daaa;
  border-right-color: #60daaa;
  animation: border 2s infinite;
}
.draw::after {
  bottom: 0;
  right: 0;
  animation: border 2s 1s infinite, borderColor 2s 1s infinite;
}

@keyframes border {
  0% {
    width: 0;
    height: 0;
  }
  25% {
    width: 100%;
    height: 0;
  }
  50% {
    width: 100%;
    height: 100%;
  }
  100% {
    width: 100%;
    height: 100%;
  }
}
@keyframes borderColor {
  0% {
    border-bottom-color: #60daaa;
    border-left-color: #60daaa;
  }
  50% {
    border-bottom-color: #60daaa;
    border-left-color: #60daaa;
  }
  51% {
    border-bottom-color: transparent;
    border-left-color: transparent;
  }
  100% {
    border-bottom-color: transparent;
    border-left-color: transparent;
  }
}

<center><h2 class="draw">Titulo</h2><center>