Hello, I posted your code and ran it. It would be fine if I changed it in two places.
first:

<Form ref="formValue" :model="formValue" :rules="formRules" :label-width="80">

v required: true, message: model = "formValue" -> : model= "formValue"
the second
{required: true, message: 'Please select the country', pattern:' /. + /', trigger: 'change'} -> {required: true, message:' Please select the country', trigger: 'change'}
the following complete code

<template>
<div class="form abs-center">

<Form ref="formValue" :model="formValue" :rules="formRules" :label-width="80">
  <FormItem label="Name" prop="name">
    <Input v-model="formValue.name" placeholder="Enter your name" />
  </FormItem>
  <FormItem label="Country" prop="country">
    <Select v-model="formValue.country" placeholder="Select your country" prop="country" @on-change="change">
      <Option value="China">China</Option>
      <Option value="U.S.A.">U.S.A.</Option>
      <Option value="Janpan">Janpan</Option>
    </Select>
  </FormItem>
</Form>
</div>
</template>

<script>
export default {
  name: "Step1",
  data() {
    return {
      formValue: {
        name: "",
        country: ""
      },
      formRules: {
        name: [
          {
            required: true,
            message: "The name cannot be empty",
            trigger: "blur"
          }
        ],
        country: [
          {
            required: true,
            message: "Please select the country",
            // pattern: "/.+/",
            trigger: "change"
          }
        ]
      }
    };
  },
};
</script>