这可以使用flutter_svg包来实现。

import 'dart:ui' as ui; // imported as ui to prevent conflict between ui.Image and the Image widget
import 'package:flutter/services.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

Future<BitmapDescriptor> _bitmapDescriptorFromSvgAsset(BuildContext context, String assetName) async {
    // Read SVG file as String
    String svgString = await DefaultAssetBundle.of(context).loadString(assetName);
    // Create DrawableRoot from SVG String
    DrawableRoot svgDrawableRoot = await svg.fromSvgString(svgString, null);

    // toPicture() and toImage() don't seem to be pixel ratio aware, so we calculate the actual sizes here
    MediaQueryData queryData = MediaQuery.of(context);
    double devicePixelRatio = queryData.devicePixelRatio;
    double width = 32 * devicePixelRatio; // where 32 is your SVG's original width
    double height = 32 * devicePixelRatio; // same thing

    // Convert to ui.Picture
    ui.Picture picture = svgDrawableRoot.toPicture(size: Size(width, height));

    // Convert to ui.Image. toImage() takes width and height as parameters
    // you need to find the best size to suit your needs and take into account the
    // screen DPI
    ui.Image image = await picture.toImage(width, height);
    ByteData bytes = await image.toByteData(format: ui.ImageByteFormat.png);
    return BitmapDescriptor.fromBytes(bytes.buffer.asUint8List());
}

然后，您可以照常使用BitmapDescriptor创建标记：

BitmapDescriptor bitmapDescriptor = await _bitmapDescriptorFromSvgAsset(context, 'assets/images/someimage.svg');
Marker marker = Marker(markerId: MarkerId('someId'), icon: bitmapDescriptor, position: LatLng(someLatitude, someLongitude));