import json
# 需要设置headers和准备payload数据

# 构建payload_headers
payload_headers = {}
payload_headers['origin'] = 'https://xxxx.com'
payload_headers[
 'user-agent'] = 'xxxxxxxx'
payload_headers['host'] = 'xxxx.com'
payload_headers['content-type'] = 'application/json;charset=UTF-8'

# 获取payload_data
payload_data = {xxx:xxx,xxx:xxx}
# payload_headers的内容就是浏览器request headers的内容。其中host和content-type是必须的

# 利用以上信息构建post请求
yield scrapy.Request(url=url, body=json.dumps(payload_data), headers=self.payload_headers,
                            callback=self.parse, dont_filter=True, method='POST')